Add server-side ELO ratings

api/QuestionsApi/Controllers/QuestionsController.cs

@@ -13,11 +13,13 @@ public class QuestionsController : ControllerBase
 {
     private readonly QuestionStore _questions;
     private readonly QuestionAttemptStore _attempts;
+    private readonly RatingStore _ratings;
 
-    public QuestionsController(QuestionStore questions, QuestionAttemptStore attempts)
+    public QuestionsController(QuestionStore questions, QuestionAttemptStore attempts, RatingStore ratings)
     {
         _questions = questions;
         _attempts = attempts;
+        _ratings = ratings;
     }
 
     [HttpGet("systems")]
@@ -34,10 +36,11 @@ public class QuestionsController : ControllerBase
     {
         var questions = await _questions.SearchAsync(req, User.IsInRole("SUPER"));
         var percentages = await _attempts.GetPercentagesByQuestionAsync(questions.Select(q => q.ExternalId));
+        var questionElos = await _ratings.GetQuestionElosAsync(questions.Select(q => q.ExternalId));
         return Ok(questions.Select(q =>
         {
             percentages.TryGetValue(q.ExternalId, out var questionPercentages);
-            return QuestionResponse.FromModel(q, questionPercentages);
+            return QuestionResponse.FromModel(q, questionPercentages, questionElos.GetValueOrDefault(q.ExternalId, 1000));
         }).ToList());
     }
 
@@ -50,7 +53,8 @@ public class QuestionsController : ControllerBase
             return NotFound();
 
         var percentages = await _attempts.GetPercentagesForQuestionAsync(question.ExternalId);
-        return Ok(QuestionResponse.FromModel(question, percentages));
+        var questionElo = await _ratings.GetQuestionEloAsync(question.ExternalId);
+        return Ok(QuestionResponse.FromModel(question, percentages, questionElo));
     }
 
     [HttpPost("attempts/first")]
@@ -75,18 +79,60 @@ public class QuestionsController : ControllerBase
         if (string.IsNullOrWhiteSpace(userId))
             return Unauthorized();
 
-        await _attempts.RecordFirstAttemptAsync(
+        var wasFirstAttempt = await _attempts.RecordFirstAttemptAsync(
             question.ExternalId,
             userId,
             req.ChoiceId.Trim(),
             req.ChoiceId.Trim() == question.CorrectChoiceId);
+        var rating = await _ratings.ApplyFirstResultAsync(
+            userId,
+            question,
+            req.ChoiceId.Trim() == question.CorrectChoiceId,
+            wasFirstAttempt);
 
         return Ok(new FirstQuestionAttemptResponse
         {
             QuestionExternalId = question.ExternalId,
             ChoiceSelectionPercentages = QuestionResponse.BuildChoiceSelectionPercentages(
                 question,
-                await _attempts.GetPercentagesForQuestionAsync(question.ExternalId))
+                await _attempts.GetPercentagesForQuestionAsync(question.ExternalId)),
+            QuestionElo = rating.QuestionElo,
+            Rating = rating
+        });
+    }
+
+    [HttpPost("{externalId}/skip")]
+    [Authorize(Roles = "USER,SUPER")]
+    public async Task<IActionResult> Skip(string externalId)
+    {
+        if (string.IsNullOrWhiteSpace(externalId))
+            return BadRequest("externalId required");
+
+        var question = await _questions.GetByExternalIdAsync(externalId.Trim());
+        if (question is null || (!question.IsPublished && !User.IsInRole("SUPER")))
+            return NotFound();
+
+        var userId = CurrentUserId();
+        if (string.IsNullOrWhiteSpace(userId))
+            return Unauthorized();
+
+        var wasFirstAttempt = await _attempts.RecordFirstAttemptAsync(
+            question.ExternalId,
+            userId,
+            "",
+            false,
+            true);
+        var rating = await _ratings.ApplyFirstResultAsync(userId, question, false, wasFirstAttempt);
+
+        return Ok(new SkipQuestionResponse
+        {
+            QuestionExternalId = question.ExternalId,
+            CorrectChoiceId = question.CorrectChoiceId,
+            ChoiceSelectionPercentages = QuestionResponse.BuildChoiceSelectionPercentages(
+                question,
+                await _attempts.GetPercentagesForQuestionAsync(question.ExternalId)),
+            QuestionElo = rating.QuestionElo,
+            Rating = rating
         });
     }
 
@@ -183,4 +229,10 @@ public class QuestionsController : ControllerBase
 
         return null;
     }
+
+    private string CurrentUserId() =>
+        User.FindFirstValue(ClaimTypes.NameIdentifier)
+        ?? User.FindFirstValue(ClaimTypes.Name)
+        ?? User.Identity?.Name
+        ?? "";
 }

api/QuestionsApi/Controllers/RatingsController.cs

@@ -0,0 +1,32 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using QuestionsApi.Services;
+using System.Security.Claims;
+
+namespace QuestionsApi.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+public class RatingsController : ControllerBase
+{
+    private readonly RatingStore _ratings;
+
+    public RatingsController(RatingStore ratings)
+    {
+        _ratings = ratings;
+    }
+
+    [HttpGet("me")]
+    [Authorize(Roles = "USER,SUPER")]
+    public async Task<IActionResult> Me()
+    {
+        var userId = User.FindFirstValue(ClaimTypes.NameIdentifier)
+            ?? User.FindFirstValue(ClaimTypes.Name)
+            ?? User.Identity?.Name
+            ?? "";
+        if (string.IsNullOrWhiteSpace(userId))
+            return Unauthorized();
+
+        return Ok(await _ratings.GetProfileAsync(userId));
+    }
+}

api/QuestionsApi/Models/Question.cs

@@ -19,6 +19,7 @@ public class Question
     public Dictionary<string, int> ChoiceSelectionPercentages { get; set; } = [];
     public string Discipline { get; set; } = "";
     public string System { get; set; } = "";
+    public string PerformanceCategory { get; set; } = "";
     public int Difficulty { get; set; } = 1;
     public List<QuestionLab> Labs { get; set; } = [];
     public List<string> Media { get; set; } = [];

api/QuestionsApi/Models/QuestionAttempt.cs

@@ -13,5 +13,6 @@ public class QuestionAttempt
     public string UserId { get; set; } = "";
     public string ChoiceId { get; set; } = "";
     public bool IsCorrect { get; set; }
+    public bool IsSkip { get; set; }
     public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
 }

api/QuestionsApi/Models/QuestionRequests.cs

@@ -22,6 +22,7 @@ public class UpsertQuestionRequest
     public Dictionary<string, int> ChoiceSelectionPercentages { get; set; } = [];
     public string Discipline { get; set; } = "";
     public string System { get; set; } = "";
+    public string PerformanceCategory { get; set; } = "";
     public int Difficulty { get; set; } = 1;
     public List<QuestionLab> Labs { get; set; } = [];
     public List<string> Media { get; set; } = [];

api/QuestionsApi/Models/QuestionResponse.cs

@@ -13,12 +13,17 @@ public class QuestionResponse
     public Dictionary<string, int> ChoiceSelectionPercentages { get; set; } = [];
     public string Discipline { get; set; } = "";
     public string System { get; set; } = "";
+    public string PerformanceCategory { get; set; } = "";
     public int Difficulty { get; set; }
+    public int QuestionElo { get; set; } = 1000;
     public List<QuestionLab> Labs { get; set; } = [];
     public List<string> Media { get; set; } = [];
     public List<string> Tags { get; set; } = [];
 
-    public static QuestionResponse FromModel(Question question, Dictionary<string, int>? liveChoiceSelectionPercentages = null) => new()
+    public static QuestionResponse FromModel(
+        Question question,
+        Dictionary<string, int>? liveChoiceSelectionPercentages = null,
+        int questionElo = 1000) => new()
     {
         Id = question.Id ?? "",
         ExternalId = question.ExternalId,
@@ -31,7 +36,9 @@ public class QuestionResponse
         ChoiceSelectionPercentages = BuildChoiceSelectionPercentages(question, liveChoiceSelectionPercentages),
         Discipline = question.Discipline,
         System = question.System,
+        PerformanceCategory = RatingCategory.Normalize(question.PerformanceCategory, question.System, question.Discipline),
         Difficulty = question.Difficulty,
+        QuestionElo = questionElo,
         Labs = question.Labs,
         Media = question.Media,
         Tags = question.Tags
@@ -52,4 +59,59 @@ public class FirstQuestionAttemptResponse
 {
     public string QuestionExternalId { get; set; } = "";
     public Dictionary<string, int> ChoiceSelectionPercentages { get; set; } = [];
+    public int QuestionElo { get; set; } = 1000;
+    public RatingChangeResponse? Rating { get; set; }
+}
+
+public class SkipQuestionResponse
+{
+    public string QuestionExternalId { get; set; } = "";
+    public string CorrectChoiceId { get; set; } = "";
+    public Dictionary<string, int> ChoiceSelectionPercentages { get; set; } = [];
+    public int QuestionElo { get; set; } = 1000;
+    public RatingChangeResponse? Rating { get; set; }
+}
+
+public static class RatingCategory
+{
+    public const string Uncategorized = "Uncategorized";
+
+    public static readonly string[] Categories =
+    [
+        "Renal/Urinary & Male/Female Systems & Pregnancy",
+        "Behavioral Health & Social Sciences: Communication, Ethics, Patient Safety",
+        "Immune/Blood & Lymphoreticular/Endocrine/Multisystem",
+        "Biostatistics & Epidemiology/Population Health",
+        "Musculoskeletal/Skin & Subcutaneous Tissue",
+        "Cardiovascular System",
+        "Nervous System & Special Senses",
+        "Respiratory System",
+        "Gastrointestinal System",
+        Uncategorized
+    ];
+
+    public static string Normalize(string? explicitCategory, string? system, string? discipline)
+    {
+        foreach (var value in new[] { explicitCategory, system, discipline })
+        {
+            if (string.IsNullOrWhiteSpace(value))
+                continue;
+            var normalized = Categories.FirstOrDefault(c => string.Equals(c, value.Trim(), StringComparison.OrdinalIgnoreCase));
+            if (normalized is not null)
+                return normalized;
+
+            var lower = value.ToLowerInvariant();
+            if (lower.Contains("cardio")) return "Cardiovascular System";
+            if (lower.Contains("resp")) return "Respiratory System";
+            if (lower.Contains("gastro") || lower.Contains("hepato")) return "Gastrointestinal System";
+            if (lower.Contains("neuro") || lower.Contains("special sense")) return "Nervous System & Special Senses";
+            if (lower.Contains("renal") || lower.Contains("urinary") || lower.Contains("pregnan") || lower.Contains("reproductive")) return "Renal/Urinary & Male/Female Systems & Pregnancy";
+            if (lower.Contains("behavior") || lower.Contains("ethic") || lower.Contains("communication") || lower.Contains("safety")) return "Behavioral Health & Social Sciences: Communication, Ethics, Patient Safety";
+            if (lower.Contains("immune") || lower.Contains("blood") || lower.Contains("endocrine") || lower.Contains("multisystem")) return "Immune/Blood & Lymphoreticular/Endocrine/Multisystem";
+            if (lower.Contains("biostat") || lower.Contains("epidemi") || lower.Contains("population")) return "Biostatistics & Epidemiology/Population Health";
+            if (lower.Contains("musculo") || lower.Contains("skin") || lower.Contains("derm")) return "Musculoskeletal/Skin & Subcutaneous Tissue";
+        }
+
+        return Uncategorized;
+    }
 }

api/QuestionsApi/Models/RatingModels.cs

@@ -0,0 +1,48 @@
+using MongoDB.Bson;
+using MongoDB.Bson.Serialization.Attributes;
+
+namespace QuestionsApi.Models;
+
+public class UserRating
+{
+    [BsonId]
+    [BsonRepresentation(BsonType.ObjectId)]
+    public string? Id { get; set; }
+
+    public string UserId { get; set; } = "";
+    public int OverallElo { get; set; } = 1000;
+    public Dictionary<string, int> CategoryElos { get; set; } = [];
+    public int RatedQuestionCount { get; set; }
+    public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
+}
+
+public class QuestionRating
+{
+    [BsonId]
+    [BsonRepresentation(BsonType.ObjectId)]
+    public string? Id { get; set; }
+
+    public string QuestionExternalId { get; set; } = "";
+    public int Elo { get; set; } = 1000;
+    public int AttemptCount { get; set; }
+    public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
+}
+
+public class RatingChangeResponse
+{
+    public bool Rated { get; set; }
+    public string Category { get; set; } = "";
+    public int UserOverallElo { get; set; }
+    public int UserOverallDelta { get; set; }
+    public int UserCategoryElo { get; set; }
+    public int UserCategoryDelta { get; set; }
+    public int QuestionElo { get; set; }
+    public int QuestionEloDelta { get; set; }
+}
+
+public class RatingProfileResponse
+{
+    public int OverallElo { get; set; }
+    public int RatedQuestionCount { get; set; }
+    public Dictionary<string, int> CategoryElos { get; set; } = [];
+}

api/QuestionsApi/Program.cs

@@ -10,6 +10,7 @@ builder.Services.AddControllers();
 
 builder.Services.AddSingleton<QuestionStore>();
 builder.Services.AddSingleton<QuestionAttemptStore>();
+builder.Services.AddSingleton<RatingStore>();
 
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen(c =>

api/QuestionsApi/Services/QuestionAttemptStore.cs

@@ -26,7 +26,7 @@ public class QuestionAttemptStore
         _col.Indexes.CreateOne(new CreateIndexModel<QuestionAttempt>(questionIndex));
     }
 
-    public async Task RecordFirstAttemptAsync(string questionExternalId, string userId, string choiceId, bool isCorrect)
+    public async Task<bool> RecordFirstAttemptAsync(string questionExternalId, string userId, string choiceId, bool isCorrect, bool isSkip = false)
     {
         var attempt = new QuestionAttempt
         {
@@ -34,15 +34,18 @@ public class QuestionAttemptStore
             UserId = userId,
             ChoiceId = choiceId,
             IsCorrect = isCorrect,
+            IsSkip = isSkip,
             CreatedUtc = DateTime.UtcNow
         };
 
         try
         {
             await _col.InsertOneAsync(attempt);
+            return true;
         }
         catch (MongoWriteException ex) when (ex.WriteError.Category == ServerErrorCategory.DuplicateKey)
         {
+            return false;
         }
     }
 
@@ -58,7 +61,7 @@ public class QuestionAttemptStore
         if (ids.Count == 0)
             return [];
 
-        var attempts = await _col.Find(a => ids.Contains(a.QuestionExternalId)).ToListAsync();
+        var attempts = await _col.Find(a => ids.Contains(a.QuestionExternalId) && !a.IsSkip).ToListAsync();
         var output = new Dictionary<string, Dictionary<string, int>>();
 
         foreach (var group in attempts.GroupBy(a => a.QuestionExternalId))

api/QuestionsApi/Services/QuestionStore.cs

@@ -139,6 +139,7 @@ public class QuestionStore
         ChoiceSelectionPercentages = req.ChoiceSelectionPercentages,
         Discipline = req.Discipline.Trim(),
         System = req.System.Trim(),
+        PerformanceCategory = RatingCategory.Normalize(req.PerformanceCategory, req.System, req.Discipline),
         Difficulty = req.Difficulty,
         Labs = req.Labs,
         Media = req.Media,

api/QuestionsApi/Services/RatingStore.cs

@@ -0,0 +1,157 @@
+using MongoDB.Driver;
+using QuestionsApi.Models;
+
+namespace QuestionsApi.Services;
+
+public class RatingStore
+{
+    private const int BaseElo = 1000;
+    private const int MinElo = 100;
+
+    private readonly IMongoCollection<UserRating> _users;
+    private readonly IMongoCollection<QuestionRating> _questions;
+
+    public RatingStore(IConfiguration cfg)
+    {
+        var cs = cfg["MongoDB:ConnectionString"] ?? "mongodb://127.0.0.1:27017";
+        var dbName = cfg["MongoDB:DatabaseName"] ?? "GameDb";
+        var client = new MongoClient(cs);
+        var db = client.GetDatabase(dbName);
+        _users = db.GetCollection<UserRating>("UserRatings");
+        _questions = db.GetCollection<QuestionRating>("QuestionRatings");
+
+        _users.Indexes.CreateOne(new CreateIndexModel<UserRating>(
+            Builders<UserRating>.IndexKeys.Ascending(r => r.UserId),
+            new CreateIndexOptions { Unique = true }));
+        _questions.Indexes.CreateOne(new CreateIndexModel<QuestionRating>(
+            Builders<QuestionRating>.IndexKeys.Ascending(r => r.QuestionExternalId),
+            new CreateIndexOptions { Unique = true }));
+    }
+
+    public async Task<RatingProfileResponse> GetProfileAsync(string userId)
+    {
+        var rating = await GetOrCreateUserRatingAsync(userId);
+        return new RatingProfileResponse
+        {
+            OverallElo = rating.OverallElo,
+            RatedQuestionCount = rating.RatedQuestionCount,
+            CategoryElos = rating.CategoryElos
+        };
+    }
+
+    public async Task<Dictionary<string, int>> GetQuestionElosAsync(IEnumerable<string> externalIds)
+    {
+        var ids = externalIds.Where(id => !string.IsNullOrWhiteSpace(id)).Distinct().ToList();
+        if (ids.Count == 0)
+            return [];
+
+        var ratings = await _questions.Find(r => ids.Contains(r.QuestionExternalId)).ToListAsync();
+        return ids.ToDictionary(
+            id => id,
+            id => ratings.FirstOrDefault(r => r.QuestionExternalId == id)?.Elo ?? BaseElo);
+    }
+
+    public async Task<int> GetQuestionEloAsync(string questionExternalId)
+    {
+        var rating = await GetOrCreateQuestionRatingAsync(questionExternalId);
+        return rating.Elo;
+    }
+
+    public async Task<RatingChangeResponse> ApplyFirstResultAsync(string userId, Question question, bool isCorrect, bool shouldRate)
+    {
+        var userRating = await GetOrCreateUserRatingAsync(userId);
+        var questionRating = await GetOrCreateQuestionRatingAsync(question.ExternalId);
+        var category = RatingCategory.Normalize(question.PerformanceCategory, question.System, question.Discipline);
+
+        if (!shouldRate)
+        {
+            return new RatingChangeResponse
+            {
+                Rated = false,
+                Category = category,
+                UserOverallElo = userRating.OverallElo,
+                UserCategoryElo = userRating.CategoryElos.GetValueOrDefault(category, BaseElo),
+                QuestionElo = questionRating.Elo
+            };
+        }
+
+        var actual = isCorrect ? 1.0 : 0.0;
+        var userK = userRating.RatedQuestionCount < 20 ? 40 : 24;
+        var questionK = questionRating.AttemptCount < 20 ? 32 : 24;
+
+        var oldOverall = userRating.OverallElo;
+        var oldCategory = userRating.CategoryElos.GetValueOrDefault(category, BaseElo);
+        var oldQuestion = questionRating.Elo;
+
+        var overallExpected = ExpectedScore(oldOverall, oldQuestion);
+        var categoryExpected = ExpectedScore(oldCategory, oldQuestion);
+        var overallDelta = (int)Math.Round(userK * (actual - overallExpected));
+        var categoryDelta = (int)Math.Round(userK * (actual - categoryExpected));
+        var questionDelta = (int)Math.Round(questionK * (overallExpected - actual));
+
+        userRating.OverallElo = Math.Max(MinElo, oldOverall + overallDelta);
+        userRating.CategoryElos[category] = Math.Max(MinElo, oldCategory + categoryDelta);
+        userRating.RatedQuestionCount++;
+        userRating.UpdatedUtc = DateTime.UtcNow;
+
+        questionRating.Elo = Math.Max(MinElo, oldQuestion + questionDelta);
+        questionRating.AttemptCount++;
+        questionRating.UpdatedUtc = DateTime.UtcNow;
+
+        await _users.ReplaceOneAsync(r => r.UserId == userRating.UserId, userRating, new ReplaceOptions { IsUpsert = true });
+        await _questions.ReplaceOneAsync(r => r.QuestionExternalId == questionRating.QuestionExternalId, questionRating, new ReplaceOptions { IsUpsert = true });
+
+        return new RatingChangeResponse
+        {
+            Rated = true,
+            Category = category,
+            UserOverallElo = userRating.OverallElo,
+            UserOverallDelta = userRating.OverallElo - oldOverall,
+            UserCategoryElo = userRating.CategoryElos[category],
+            UserCategoryDelta = userRating.CategoryElos[category] - oldCategory,
+            QuestionElo = questionRating.Elo,
+            QuestionEloDelta = questionRating.Elo - oldQuestion
+        };
+    }
+
+    private async Task<UserRating> GetOrCreateUserRatingAsync(string userId)
+    {
+        var rating = await _users.Find(r => r.UserId == userId).FirstOrDefaultAsync();
+        if (rating is null)
+        {
+            rating = new UserRating { UserId = userId, CategoryElos = DefaultCategoryElos() };
+            await _users.InsertOneAsync(rating);
+            return rating;
+        }
+
+        var changed = false;
+        foreach (var category in RatingCategory.Categories)
+        {
+            if (!rating.CategoryElos.ContainsKey(category))
+            {
+                rating.CategoryElos[category] = BaseElo;
+                changed = true;
+            }
+        }
+        if (changed)
+            await _users.ReplaceOneAsync(r => r.UserId == userId, rating);
+        return rating;
+    }
+
+    private async Task<QuestionRating> GetOrCreateQuestionRatingAsync(string questionExternalId)
+    {
+        var rating = await _questions.Find(r => r.QuestionExternalId == questionExternalId).FirstOrDefaultAsync();
+        if (rating is not null)
+            return rating;
+
+        rating = new QuestionRating { QuestionExternalId = questionExternalId };
+        await _questions.InsertOneAsync(rating);
+        return rating;
+    }
+
+    private static Dictionary<string, int> DefaultCategoryElos() =>
+        RatingCategory.Categories.ToDictionary(category => category, _ => BaseElo);
+
+    private static double ExpectedScore(int playerElo, int questionElo) =>
+        1.0 / (1.0 + Math.Pow(10.0, (questionElo - playerElo) / 400.0));
+}

scripts/autoload/block_session_service.gd

@@ -130,6 +130,29 @@ func submit_core_attempt(choice_id: String, eliminated: Array, flagged: bool) ->
 	}
 
 
+func skip_core_question(eliminated: Array, flagged: bool) -> Dictionary:
+	var question := get_current_question()
+	if question.is_empty():
+		return {}
+
+	var answer := {
+		"question": question.duplicate(true),
+		"selected_choice_id": "",
+		"is_correct": false,
+		"is_skip": true,
+		"eliminated_choice_ids": eliminated.duplicate(),
+		"flagged": flagged,
+		"elapsed_seconds": get_current_elapsed_seconds(),
+		"target_seconds": core_current_target_seconds
+	}
+	answers[current_index] = answer
+	ProfileService.record_wrong_attempt(question)
+	_apply_core_wrong_penalty(answer)
+	core_target_seconds = min(CORE_MAX_TARGET_SECONDS, core_target_seconds * 1.05)
+	session_changed.emit()
+	return answer
+
+
 func move_previous() -> bool:
 	if current_index > 0:
 		current_index -= 1
@@ -207,6 +230,15 @@ func update_question_choice_percentages(question_id: String, percentages: Dictio
 			break
 
 
+func update_question_elo(question_id: String, question_elo: int) -> void:
+	for index in range(active_questions.size()):
+		var question: Dictionary = active_questions[index]
+		if str(question.get("id", "")) == question_id:
+			question["question_elo"] = question_elo
+			active_questions[index] = question
+			break
+
+
 func advance_core_question() -> bool:
 	var question := _draw_core_question()
 	if question.is_empty():

scripts/autoload/profile_service.gd

@@ -62,12 +62,9 @@ func get_profile() -> Dictionary:
 
 func apply_block_results(results: Dictionary) -> void:
 	_ensure_daily_current()
-	profile["xp"] = int(profile["xp"]) + int(results.get("xp_earned", 0))
-	profile["level"] = ProgressionService.level_for_xp(int(profile["xp"]))
 	profile["current_streak"] = int(results.get("ending_streak", profile["current_streak"]))
 	profile["best_streak"] = max(int(profile["best_streak"]), int(profile["current_streak"]))
 	profile["daily_questions_answered"] = int(profile["daily_questions_answered"]) + int(results.get("total", 0))
-	profile["daily_xp_earned"] = int(profile["daily_xp_earned"]) + int(results.get("xp_earned", 0))
 
 	var unlocked_badges: Array = results.get("badges_unlocked", [])
 	for badge in unlocked_badges:
@@ -91,7 +88,7 @@ func apply_block_results(results: Dictionary) -> void:
 		"system": results.get("system", "All Systems"),
 		"correct": results.get("correct", 0),
 		"total": results.get("total", 0),
-		"xp_earned": results.get("xp_earned", 0)
+		"xp_earned": 0
 	}
 	profile["block_history"].push_front(summary)
 	if profile["block_history"].size() > 12:
@@ -135,12 +132,9 @@ func reset_qbank_memory() -> void:
 
 func apply_question_results(results: Dictionary) -> void:
 	_ensure_daily_current()
-	profile["xp"] = int(profile["xp"]) + int(results.get("xp_earned", 0))
-	profile["level"] = ProgressionService.level_for_xp(int(profile["xp"]))
 	profile["current_streak"] = int(results.get("ending_streak", profile["current_streak"]))
 	profile["best_streak"] = max(int(profile["best_streak"]), int(profile["current_streak"]))
 	profile["daily_questions_answered"] = int(profile["daily_questions_answered"]) + int(results.get("total", 0))
-	profile["daily_xp_earned"] = int(profile["daily_xp_earned"]) + int(results.get("xp_earned", 0))
 
 	var unlocked_badges: Array = results.get("badges_unlocked", [])
 	for badge in unlocked_badges:

scripts/autoload/question_bank_service.gd

@@ -2,27 +2,42 @@ extends Node
 
 const DEFAULT_QUESTIONS_API_URL := "https://s3q.ranaze.com/api/questions/search"
 const DEFAULT_QUESTION_ATTEMPT_API_URL := "https://s3q.ranaze.com/api/questions/attempts/first"
+const DEFAULT_QUESTION_API_BASE_URL := "https://s3q.ranaze.com/api/questions"
+const DEFAULT_RATINGS_API_URL := "https://s3q.ranaze.com/api/ratings/me"
 const RETRY_DELAYS := [2, 5, 10, 20, 30]
 
 signal questions_changed
 signal questions_load_failed(message: String)
 signal choice_percentages_updated(question_id: String, percentages: Dictionary)
+signal ratings_changed
+signal question_rating_updated(question_id: String, question_elo: int, rating: Dictionary)
+signal question_skipped(question_id: String, correct_choice_id: String, question_elo: int, rating: Dictionary)
 
 var questions: Array = []
 var request: HTTPRequest
 var attempt_request: HTTPRequest
+var rating_request: HTTPRequest
+var skip_request: HTTPRequest
 var retry_timer: Timer
 var questions_api_url := DEFAULT_QUESTIONS_API_URL
 var question_attempt_api_url := DEFAULT_QUESTION_ATTEMPT_API_URL
+var question_api_base_url := DEFAULT_QUESTION_API_BASE_URL
+var ratings_api_url := DEFAULT_RATINGS_API_URL
 var is_loading := false
 var last_error := ""
 var load_state := "idle"
 var retry_attempt := 0
 var next_retry_seconds := 0
+var overall_elo := 1000
+var rated_question_count := 0
+var category_elos := {}
+var last_rating_change := {}
 
 func _ready() -> void:
 	questions_api_url = str(ProjectSettings.get_setting("step3/questions_api_url", DEFAULT_QUESTIONS_API_URL))
 	question_attempt_api_url = str(ProjectSettings.get_setting("step3/question_attempt_api_url", DEFAULT_QUESTION_ATTEMPT_API_URL))
+	question_api_base_url = str(ProjectSettings.get_setting("step3/question_api_base_url", DEFAULT_QUESTION_API_BASE_URL))
+	ratings_api_url = str(ProjectSettings.get_setting("step3/ratings_api_url", DEFAULT_RATINGS_API_URL))
 	request = HTTPRequest.new()
 	request.request_completed.connect(_on_api_questions_loaded)
 	add_child(request)
@@ -31,6 +46,14 @@ func _ready() -> void:
 	attempt_request.request_completed.connect(_on_first_attempt_recorded)
 	add_child(attempt_request)
 
+	rating_request = HTTPRequest.new()
+	rating_request.request_completed.connect(_on_ratings_loaded)
+	add_child(rating_request)
+
+	skip_request = HTTPRequest.new()
+	skip_request.request_completed.connect(_on_question_skipped)
+	add_child(skip_request)
+
 	retry_timer = Timer.new()
 	retry_timer.one_shot = true
 	retry_timer.timeout.connect(_on_retry_timer_timeout)
@@ -52,6 +75,7 @@ func load_questions_from_api(reset_retry: bool = true) -> void:
 	last_error = ""
 	questions.clear()
 	questions_changed.emit()
+	load_ratings_from_api()
 
 	var headers := PackedStringArray([
 		"Content-Type: application/json",
@@ -107,6 +131,10 @@ func clear_questions() -> void:
 		request.cancel_request()
 	if attempt_request != null:
 		attempt_request.cancel_request()
+	if rating_request != null:
+		rating_request.cancel_request()
+	if skip_request != null:
+		skip_request.cancel_request()
 	if retry_timer != null:
 		retry_timer.stop()
 	questions.clear()
@@ -115,7 +143,12 @@ func clear_questions() -> void:
 	load_state = "idle"
 	retry_attempt = 0
 	next_retry_seconds = 0
+	overall_elo = 1000
+	rated_question_count = 0
+	category_elos = {}
+	last_rating_change = {}
 	questions_changed.emit()
+	ratings_changed.emit()
 
 
 func record_first_attempt(question_id: String, choice_id: String) -> void:
@@ -135,6 +168,31 @@ func record_first_attempt(question_id: String, choice_id: String) -> void:
 		push_warning("Failed to record first question attempt.")
 
 
+func skip_question(question_id: String) -> void:
+	if AuthState.access_token.is_empty() or question_id == "":
+		return
+
+	var headers := PackedStringArray([
+		"Content-Type: application/json",
+		"Authorization: Bearer %s" % AuthState.access_token
+	])
+	var url := "%s/%s/skip" % [question_api_base_url.rstrip("/"), question_id.uri_encode()]
+	var err := skip_request.request(url, headers, HTTPClient.METHOD_POST, "")
+	if err != OK:
+		push_warning("Failed to record skipped question.")
+
+
+func load_ratings_from_api() -> void:
+	if AuthState.access_token.is_empty():
+		return
+	var headers := PackedStringArray([
+		"Authorization: Bearer %s" % AuthState.access_token
+	])
+	var err := rating_request.request(ratings_api_url, headers, HTTPClient.METHOD_GET)
+	if err != OK:
+		push_warning("Failed to request rating profile.")
+
+
 func get_all_questions() -> Array:
 	return questions.duplicate(true)
 
@@ -214,7 +272,53 @@ func _on_first_attempt_recorded(result: int, response_code: int, _headers: Packe
 		return
 
 	_update_question_percentages(question_id, percentages)
+	var question_elo := int(parsed.get("questionElo", parsed.get("question_elo", 1000)))
+	var rating: Dictionary = parsed.get("rating", {})
+	_update_question_elo(question_id, question_elo)
+	_apply_rating_change(rating)
 	choice_percentages_updated.emit(question_id, percentages)
+	question_rating_updated.emit(question_id, question_elo, rating)
+
+
+func _on_question_skipped(result: int, response_code: int, _headers: PackedStringArray, body: PackedByteArray) -> void:
+	if result != HTTPRequest.RESULT_SUCCESS or response_code < 200 or response_code >= 300:
+		push_warning("Question skip API request failed with status %d." % response_code)
+		return
+
+	var parsed: Variant = JSON.parse_string(body.get_string_from_utf8())
+	if typeof(parsed) != TYPE_DICTIONARY:
+		push_warning("Question skip API response was not an object.")
+		return
+
+	var question_id := str(parsed.get("questionExternalId", parsed.get("question_external_id", "")))
+	var correct_choice_id := str(parsed.get("correctChoiceId", parsed.get("correct_choice_id", "")))
+	var percentages: Dictionary = parsed.get("choiceSelectionPercentages", parsed.get("choice_selection_percentages", {}))
+	var question_elo := int(parsed.get("questionElo", parsed.get("question_elo", 1000)))
+	var rating: Dictionary = parsed.get("rating", {})
+	if question_id == "":
+		return
+
+	_update_question_percentages(question_id, percentages)
+	_update_question_elo(question_id, question_elo)
+	_apply_rating_change(rating)
+	choice_percentages_updated.emit(question_id, percentages)
+	question_skipped.emit(question_id, correct_choice_id, question_elo, rating)
+
+
+func _on_ratings_loaded(result: int, response_code: int, _headers: PackedStringArray, body: PackedByteArray) -> void:
+	if result != HTTPRequest.RESULT_SUCCESS or response_code < 200 or response_code >= 300:
+		push_warning("Ratings API request failed with status %d." % response_code)
+		return
+
+	var parsed: Variant = JSON.parse_string(body.get_string_from_utf8())
+	if typeof(parsed) != TYPE_DICTIONARY:
+		push_warning("Ratings API response was not an object.")
+		return
+
+	overall_elo = int(parsed.get("overallElo", parsed.get("overall_elo", 1000)))
+	rated_question_count = int(parsed.get("ratedQuestionCount", parsed.get("rated_question_count", 0)))
+	category_elos = parsed.get("categoryElos", parsed.get("category_elos", {}))
+	ratings_changed.emit()
 
 
 func _update_question_percentages(question_id: String, percentages: Dictionary) -> void:
@@ -226,6 +330,27 @@ func _update_question_percentages(question_id: String, percentages: Dictionary)
 			return
 
 
+func _update_question_elo(question_id: String, question_elo: int) -> void:
+	for index in range(questions.size()):
+		var question: Dictionary = questions[index]
+		if str(question.get("id", "")) == question_id:
+			question["question_elo"] = question_elo
+			questions[index] = question
+			return
+
+
+func _apply_rating_change(rating: Dictionary) -> void:
+	if rating.is_empty():
+		return
+	last_rating_change = rating
+	overall_elo = int(rating.get("userOverallElo", rating.get("user_overall_elo", overall_elo)))
+	var category := str(rating.get("category", ""))
+	if category != "":
+		category_elos[category] = int(rating.get("userCategoryElo", rating.get("user_category_elo", category_elos.get(category, 1000))))
+	rated_question_count += 1 if bool(rating.get("rated", false)) else 0
+	ratings_changed.emit()
+
+
 func _is_valid_question(item: Variant) -> bool:
 	if typeof(item) != TYPE_DICTIONARY:
 		return false
@@ -252,7 +377,9 @@ func _normalize_api_question(item: Variant) -> Dictionary:
 		"choice_selection_percentages": item.get("choiceSelectionPercentages", item.get("choice_selection_percentages", {})),
 		"discipline": str(item.get("discipline", "")),
 		"system": str(item.get("system", "")),
+		"performance_category": str(item.get("performanceCategory", item.get("performance_category", ""))),
 		"difficulty": int(item.get("difficulty", 1)),
+		"question_elo": int(item.get("questionElo", item.get("question_elo", 1000))),
 		"labs": item.get("labs", []),
 		"media": item.get("media", []),
 		"tags": item.get("tags", [])

scripts/ui/dashboard.gd

@@ -5,7 +5,7 @@ const Style := preload("res://scripts/ui/ui_style.gd")
 var main: Control
 var status_label: Label
 var daily_label: Label
-var xp_label: Label
+var elo_label: Label
 var streak_label: Label
 var bank_label: Label
 var error_label: Label
@@ -17,6 +17,8 @@ func _ready() -> void:
 	add_theme_constant_override("separation", 18)
 	if not QuestionBankService.questions_changed.is_connected(_refresh):
 		QuestionBankService.questions_changed.connect(_refresh)
+	if not QuestionBankService.ratings_changed.is_connected(_refresh):
+		QuestionBankService.ratings_changed.connect(_refresh)
 	if not ProfileService.profile_changed.is_connected(_refresh):
 		ProfileService.profile_changed.connect(_refresh)
 
@@ -36,7 +38,7 @@ func _ready() -> void:
 	add_child(summary)
 
 	daily_label = _add_metric(summary, "Today")
-	xp_label = _add_metric(summary, "Daily XP")
+	elo_label = _add_metric(summary, "ELO")
 	streak_label = _add_metric(summary, "Streak")
 	bank_label = _add_metric(summary, "Question Bank")
 
@@ -115,7 +117,10 @@ func _refresh() -> void:
 	if progress > 100:
 		progress = 100
 	daily_label.text = "Today\n%d/%d questions\n%d%% complete" % [answered, goal, progress]
-	xp_label.text = "Daily XP\n%d XP earned" % int(profile.get("daily_xp_earned", 0))
+	elo_label.text = "ELO\n%d overall\n%d rated" % [
+		QuestionBankService.overall_elo,
+		QuestionBankService.rated_question_count
+	]
 	streak_label.text = "Streak\n%d current\n%d best" % [
 		int(profile.get("current_streak", 0)),
 		int(profile.get("best_streak", 0))

scripts/ui/main.gd

@@ -131,6 +131,7 @@ func _build_ui() -> void:
 	screens["profile"] = profile
 
 	ProfileService.profile_changed.connect(_refresh_header_stats)
+	QuestionBankService.ratings_changed.connect(_refresh_header_stats)
 	AuthState.auth_changed.connect(_refresh_header_stats)
 	_refresh_header_stats()
 	_build_app_menu()
@@ -148,9 +149,8 @@ func _refresh_header_stats() -> void:
 	if header_stats == null:
 		return
 	var profile := ProfileService.get_profile()
-	header_stats.text = "LV %d  |  %d XP  |  Streak %d" % [
-		profile.get("level", 1),
-		profile.get("xp", 0),
+	header_stats.text = "ELO %d  |  Streak %d" % [
+		QuestionBankService.overall_elo,
 		profile.get("current_streak", 0)
 	]
 	if user_label != null:

scripts/ui/main_menu.gd

@@ -10,7 +10,7 @@ func _ready() -> void:
 	add_theme_constant_override("separation", 18)
 
 	var headline := Label.new()
-	headline.text = "Answer board-style questions. Earn XP. Unlock the map."
+	headline.text = "Answer board-style questions. Raise your ELO. Unlock the map."
 	headline.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
 	Style.set_label(headline, 38, Style.TEXT)
 	add_child(headline)
@@ -31,7 +31,7 @@ func _ready() -> void:
 	hero.add_child(hero_content)
 
 	var loop := Label.new()
-	loop.text = "XP Rush  |  Streak Heat  |  System Zones  |  Timed Blocks"
+	loop.text = "ELO Climb  |  Streak Heat  |  System Zones  |  Timed Blocks"
 	Style.set_label(loop, 24, Style.CYAN)
 	hero_content.add_child(loop)
 
@@ -72,9 +72,8 @@ func _ready() -> void:
 
 func on_show(_payload: Variant = null) -> void:
 	var profile := ProfileService.get_profile()
-	stats_label.text = "Level %d  |  %d XP  |  Current streak: %d  |  Badges: %d" % [
-		profile["level"],
-		profile["xp"],
+	stats_label.text = "ELO %d  |  Current streak: %d  |  Badges: %d" % [
+		QuestionBankService.overall_elo,
 		profile["current_streak"],
 		profile["badges"].size()
 	]

scripts/ui/progress_profile.gd

@@ -52,23 +52,21 @@ func _ready() -> void:
 func on_show(_payload: Variant = null) -> void:
 	_reset_qbank_confirmation()
 	var profile := ProfileService.get_profile()
-	var xp_into := ProgressionService.xp_into_level(int(profile["xp"]))
-	var text := "[b]Level %d[/b]\n%d total XP (%d/%d to next level)\nCurrent streak: %d\nBest streak: %d\nToday: %d/%d questions, +%d XP\n\n[b]Badges[/b]\n" % [
-		profile["level"],
-		profile["xp"],
-		xp_into,
-		ProgressionService.XP_PER_LEVEL,
+	var text := "[b]Overall ELO %d[/b]\n%d rated questions\nCurrent streak: %d\nBest streak: %d\nToday: %d/%d questions\n\n[b]Category ELO[/b]\n" % [
+		QuestionBankService.overall_elo,
+		QuestionBankService.rated_question_count,
 		profile["current_streak"],
 		profile["best_streak"],
 		profile.get("daily_questions_answered", 0),
-		profile.get("daily_goal_questions", 10),
-		profile.get("daily_xp_earned", 0)
+		profile.get("daily_goal_questions", 10)
 	]
-	if profile["badges"].is_empty():
-		text += "No badges yet.\n"
+	if QuestionBankService.category_elos.is_empty():
+		text += "No rated categories yet.\n"
 	else:
-		for badge in profile["badges"]:
-			text += "- %s\n" % badge
+		var categories := QuestionBankService.category_elos.keys()
+		categories.sort()
+		for category in categories:
+			text += "- %s: %d\n" % [category, int(QuestionBankService.category_elos[category])]
 
 	text += "\n[b]System Accuracy[/b]\n"
 	if profile["system_stats"].is_empty():
@@ -83,12 +81,11 @@ func on_show(_payload: Variant = null) -> void:
 
 	text += "\n[b]Recent Blocks[/b]\n"
 	for block in profile["block_history"]:
-		text += "- %s: %s %d/%d, +%d XP\n" % [
+		text += "- %s: %s %d/%d\n" % [
 			block.get("timestamp", ""),
 			block.get("system", ""),
 			block.get("correct", 0),
-			block.get("total", 0),
-			block.get("xp_earned", 0)
+			block.get("total", 0)
 		]
 	profile_text.text = text
 

scripts/ui/question_player.gd

@@ -6,6 +6,7 @@ const CORRECT_ADVANCE_DELAY_SECONDS := 0.6
 
 var main: Control
 var choice_buttons: Array[Button] = []
+var choice_percent_labels: Array[Label] = []
 var eliminated: Array = []
 var locked_wrong_choice_ids: Array = []
 var flagged := false
@@ -23,7 +24,9 @@ var timer_label: Label
 var stem_label: RichTextLabel
 var lead_label: Label
 var explanation_label: RichTextLabel
+var question_elo_label: Label
 var next_button: Button
+var skip_button: Button
 var flag_button: Button
 var report_button: Button
 var nav_palette: HBoxContainer
@@ -41,6 +44,10 @@ func _ready() -> void:
 	add_theme_constant_override("separation", 10)
 	if not QuestionBankService.choice_percentages_updated.is_connected(_on_choice_percentages_updated):
 		QuestionBankService.choice_percentages_updated.connect(_on_choice_percentages_updated)
+	if not QuestionBankService.question_rating_updated.is_connected(_on_question_rating_updated):
+		QuestionBankService.question_rating_updated.connect(_on_question_rating_updated)
+	if not QuestionBankService.question_skipped.is_connected(_on_question_skipped):
+		QuestionBankService.question_skipped.connect(_on_question_skipped)
 
 	var top := HBoxContainer.new()
 	top.add_theme_constant_override("separation", 12)
@@ -125,6 +132,12 @@ func _ready() -> void:
 	Style.set_label(lead_label, 21, Style.TEXT)
 	question_content.add_child(lead_label)
 
+	question_elo_label = Label.new()
+	question_elo_label.visible = false
+	question_elo_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_RIGHT
+	Style.set_label(question_elo_label, 16, Style.AMBER)
+	question_content.add_child(question_elo_label)
+
 	for index in range(5):
 		var button := Button.new()
 		button.custom_minimum_size = Vector2(0, 64)
@@ -133,6 +146,19 @@ func _ready() -> void:
 		button.pressed.connect(func(i := index): _select_choice(i))
 		button.gui_input.connect(func(event: InputEvent, i := index): _choice_gui_input(event, i))
 		choice_buttons.append(button)
+
+		var percent_label := Label.new()
+		percent_label.visible = false
+		percent_label.mouse_filter = Control.MOUSE_FILTER_IGNORE
+		percent_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_RIGHT
+		percent_label.vertical_alignment = VERTICAL_ALIGNMENT_CENTER
+		percent_label.set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
+		percent_label.offset_left = 0
+		percent_label.offset_right = -18
+		Style.set_label(percent_label, 18, Style.TEXT)
+		button.add_child(percent_label)
+		choice_percent_labels.append(percent_label)
+
 		question_content.add_child(button)
 
 	explanation_label = RichTextLabel.new()
@@ -145,6 +171,13 @@ func _ready() -> void:
 
 	var actions := HBoxContainer.new()
 	actions.add_theme_constant_override("separation", 10)
+	skip_button = Button.new()
+	skip_button.text = "Skip"
+	skip_button.custom_minimum_size = Vector2(120, 48)
+	Style.style_chip(skip_button, Style.AMBER)
+	skip_button.pressed.connect(_skip_current_question)
+	actions.add_child(skip_button)
+
 	next_button = Button.new()
 	next_button.text = "Submit"
 	next_button.custom_minimum_size = Vector2(140, 48)
@@ -215,7 +248,12 @@ func _load_question() -> void:
 	flag_button.button_pressed = false
 	_refresh_toolbar_state()
 	explanation_label.visible = false
+	question_elo_label.visible = false
+	question_elo_label.text = ""
 	next_button.text = "Submit"
+	next_button.disabled = false
+	skip_button.disabled = false
+	skip_button.visible = BlockSessionService.session_kind == "core"
 
 	var question := BlockSessionService.get_current_question()
 	if question.is_empty():
@@ -255,6 +293,7 @@ func _load_question() -> void:
 		else:
 			_apply_saved_choice_state()
 			next_button.text = "Next"
+		_update_question_elo_label(true)
 
 	_refresh_nav_palette()
 	_refresh_toolbar_state()
@@ -276,6 +315,25 @@ func _select_choice(index: int) -> void:
 	_apply_saved_choice_state()
 
 
+func _skip_current_question() -> void:
+	if pending_correct_advance or not current_answer.is_empty() or BlockSessionService.session_kind != "core":
+		return
+	var question_id := str(BlockSessionService.get_current_question().get("id", ""))
+	if question_id == "":
+		return
+	current_answer = BlockSessionService.skip_core_question(eliminated, flagged)
+	if current_answer.is_empty():
+		return
+	QuestionBankService.skip_question(question_id)
+	selected_choice = ""
+	next_button.disabled = true
+	skip_button.disabled = true
+	pending_correct_advance = true
+	correct_advance_delay = CORRECT_ADVANCE_DELAY_SECONDS
+	_show_explanation()
+	_update_question_elo_label(true)
+
+
 func _choice_gui_input(event: InputEvent, index: int) -> void:
 	if pending_correct_advance:
 		return
@@ -333,6 +391,7 @@ func _submit_or_next() -> void:
 			var answer: Dictionary = result.get("answer", {})
 			if bool(result.get("is_correct", false)):
 				current_answer = answer
+				_update_question_elo_label(true)
 				_trigger_correct_feedback()
 				return
 			_lock_wrong_choice(attempted_choice)
@@ -361,6 +420,7 @@ func _show_explanation() -> void:
 	for index in range(question.get("choices", []).size()):
 		var choice: Dictionary = question["choices"][index]
 		var id := str(choice.get("id", ""))
+		_set_choice_button_text(index, choice)
 		if id == correct_id:
 			choice_buttons[index].modulate = Color(0.54, 1.0, 0.58)
 		elif id == selected_choice:
@@ -369,6 +429,7 @@ func _show_explanation() -> void:
 	var result_text := "Correct" if current_answer.get("is_correct", false) else "Incorrect"
 	explanation_label.text = "[b]%s[/b]\n%s" % [result_text, question.get("explanation", "")]
 	explanation_label.visible = true
+	_update_question_elo_label(true)
 	_refresh_nav_palette()
 
 
@@ -434,6 +495,8 @@ func _trigger_correct_feedback() -> void:
 	red_fog_time = 0.0
 	green_fog_time = FEEDBACK_FADE_SECONDS
 	next_button.disabled = true
+	if skip_button != null:
+		skip_button.disabled = true
 	for button in choice_buttons:
 		button.disabled = true
 	if feedback_fog != null:
@@ -462,6 +525,8 @@ func _update_answer_feedback(delta: float) -> void:
 		if correct_advance_delay <= 0.0:
 			pending_correct_advance = false
 			next_button.disabled = false
+			if skip_button != null:
+				skip_button.disabled = false
 			_advance_or_finish()
 
 
@@ -474,6 +539,8 @@ func _reset_wrong_feedback() -> void:
 	correct_advance_delay = 0.0
 	pending_correct_advance = false
 	next_button.disabled = false
+	if skip_button != null:
+		skip_button.disabled = false
 	if feedback_fog != null:
 		feedback_fog.color = Color(1.0, 0.0, 0.0, 0.0)
 
@@ -596,22 +663,38 @@ func _apply_saved_choice_state() -> void:
 		else:
 			choice_buttons[index].modulate = Color.WHITE
 
+	if pending_correct_advance:
+		_apply_correct_answer_preview()
+
 
 func _set_choice_button_text(index: int, choice: Dictionary) -> void:
 	var choice_id := str(choice.get("id", ""))
 	var choice_text := str(choice.get("text", ""))
+	_set_choice_percent_label(index, "")
 	if locked_wrong_choice_ids.has(choice_id):
-		var text := "%s. %s" % [choice_id, _strike_text(choice_text)]
 		var percentage := _get_choice_selection_percentage(choice_id)
 		if percentage >= 0:
-			text += "\n   %d%%" % percentage
-		choice_buttons[index].text = text
+			_set_choice_percent_label(index, "%d%%" % percentage)
+		choice_buttons[index].text = "%s. %s" % [choice_id, _strike_text(choice_text)]
+	elif _should_show_correct_choice_percentage(choice_id):
+		var correct_percentage := _get_choice_selection_percentage(choice_id)
+		if correct_percentage >= 0:
+			_set_choice_percent_label(index, "%d%%" % correct_percentage)
+		choice_buttons[index].text = "%s. %s" % [choice_id, choice_text]
 	elif eliminated.has(choice_id):
 		choice_buttons[index].text = "%s. [eliminated] %s" % [choice_id, _strike_text(choice_text)]
 	else:
 		choice_buttons[index].text = "%s. %s" % [choice_id, choice_text]
 
 
+func _set_choice_percent_label(index: int, text: String) -> void:
+	if index < 0 or index >= choice_percent_labels.size():
+		return
+	var label := choice_percent_labels[index]
+	label.text = text
+	label.visible = text != ""
+
+
 func _get_choice_selection_percentage(choice_id: String) -> int:
 	var question := BlockSessionService.get_current_question()
 	var percentages: Dictionary = question.get("choice_selection_percentages", {})
@@ -622,6 +705,21 @@ func _get_choice_selection_percentage(choice_id: String) -> int:
 	return clamp(int(percentages.get(choice_id, -1)), 0, 100)
 
 
+func _should_show_correct_choice_percentage(choice_id: String) -> bool:
+	var question := BlockSessionService.get_current_question()
+	return choice_id == str(question.get("correct_choice_id", "")) and (pending_correct_advance or not current_answer.is_empty())
+
+
+func _apply_correct_answer_preview() -> void:
+	var question := BlockSessionService.get_current_question()
+	var correct_id := str(question.get("correct_choice_id", ""))
+	var choices: Array = question.get("choices", [])
+	for index in range(choices.size()):
+		if str(choices[index].get("id", "")) == correct_id:
+			choice_buttons[index].modulate = Color(0.54, 1.0, 0.58)
+			return
+
+
 func _on_choice_percentages_updated(question_id: String, percentages: Dictionary) -> void:
 	if not visible:
 		return
@@ -631,6 +729,37 @@ func _on_choice_percentages_updated(question_id: String, percentages: Dictionary
 	_apply_saved_choice_state()
 
 
+func _on_question_rating_updated(question_id: String, question_elo: int, _rating: Dictionary) -> void:
+	if str(BlockSessionService.get_current_question().get("id", "")) != question_id:
+		return
+	BlockSessionService.update_question_elo(question_id, question_elo)
+	_update_question_elo_label(not current_answer.is_empty() or pending_correct_advance)
+	_apply_saved_choice_state()
+
+
+func _on_question_skipped(question_id: String, correct_choice_id: String, question_elo: int, _rating: Dictionary) -> void:
+	if str(BlockSessionService.get_current_question().get("id", "")) != question_id:
+		return
+	var question := BlockSessionService.get_current_question()
+	if correct_choice_id != "":
+		question["correct_choice_id"] = correct_choice_id
+	BlockSessionService.update_question_elo(question_id, question_elo)
+	_update_question_elo_label(true)
+	_apply_saved_choice_state()
+
+
+func _update_question_elo_label(show_label: bool) -> void:
+	if question_elo_label == null:
+		return
+	if not show_label:
+		question_elo_label.visible = false
+		return
+	var question := BlockSessionService.get_current_question()
+	var question_elo := int(question.get("question_elo", 1000))
+	question_elo_label.text = "Question ELO %d" % question_elo
+	question_elo_label.visible = true
+
+
 func _strike_text(value: String) -> String:
 	var result := ""
 	for character in value:

scripts/ui/review_results.gd

@@ -48,11 +48,10 @@ func _ready() -> void:
 func on_show(payload: Variant = null) -> void:
 	var results: Dictionary = payload if typeof(payload) == TYPE_DICTIONARY else {}
 	var accuracy := int(round(float(results.get("accuracy", 0.0)) * 100.0))
-	summary_label.text = "%d/%d correct (%d%%)  |  +%d XP  |  Streak: %d  |  New badges: %s" % [
+	summary_label.text = "%d/%d correct (%d%%)  |  Streak: %d  |  New badges: %s" % [
 		results.get("correct", 0),
 		results.get("total", 0),
 		accuracy,
-		results.get("xp_earned", 0),
 		results.get("ending_streak", 0),
 		", ".join(results.get("badges_unlocked", [])) if results.get("badges_unlocked", []).size() > 0 else "None"
 	]

scripts/ui/study_map.gd

@@ -17,7 +17,7 @@ func _ready() -> void:
 	add_child(title)
 
 	var help := Label.new()
-	help.text = "Choose a system zone. Strong scores unlock momentum badges and level progress."
+	help.text = "Choose a system zone. Strong scores raise your rating and build momentum."
 	help.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
 	Style.set_label(help, 16, Style.MUTED)
 	add_child(help)