Add an RZ Coin slot machine

Adds a spend-coins-for-a-random-reward mini-game reachable from the
shop. Backend mirrors the store's existing atomic/idempotent purchase
pattern (SpinAsync in CreditStore.cs) with a server-authoritative,
weighted reward roll and a rolling per-user spin-rate guard; odds are
served from GET /api/credits/spin-config so the client never hardcodes
numbers that could drift from the real payout table. The mockup's
"Streak Protector" reward was swapped for a real Exam Simulation Token
since streaks aren't currently a persisted, protectable concept.

Also fixes two latent bugs surfaced while building this:
- credits_service.gd's operation-id builder referenced a nonexistent
  AuthState.user_id (should be .username), throwing on every credit
  action.
- _post() silently no-op'd with no signal when signed out, which
  combined with a GDScript closure gotcha (lambdas capture outer
  locals by value, so reassigning inside one never reached the
  caller) meant a spin attempted while unauthenticated could hang
  forever instead of surfacing an error.

api/QuestionsApi/Controllers/CreditsController.cs

@@ -48,6 +48,27 @@ public sealed class CreditsController(CreditStore credits, ExamSimulationStore s
                 { code = "reset_token_required", message = "A QBank Reset Token is required.", credits = result.Status });
     }
 
+    [HttpGet("spin-config")]
+    public IActionResult SpinConfig() => Ok(new SpinConfigResponse());
+
+    [HttpPost("spin")]
+    public async Task<IActionResult> Spin([FromBody] SpinRequest request)
+    {
+        if (!ValidOperationId(request.OperationId))
+            return BadRequest(new { code = "invalid_operation_id", message = "A valid operation ID is required." });
+        var result = await credits.SpinAsync(UserId(), request.OperationId);
+        return result.Result switch
+        {
+            CreditOperationResult.Succeeded => Ok(result),
+            CreditOperationResult.InsufficientCredits => Conflict(new
+                { code = "insufficient_coins", message = "Not enough Rz Coins.", credits = result.Status }),
+            CreditOperationResult.RateLimited => Conflict(new
+                { code = "rate_limited", message = "Too many spins - try again later.", credits = result.Status }),
+            _ => Conflict(new
+                { code = "operation_conflict", message = "That operation ID was already used.", credits = result.Status })
+        };
+    }
+
     private string UserId() => User.FindFirstValue(ClaimTypes.NameIdentifier)
         ?? User.FindFirstValue(ClaimTypes.Name)
         ?? User.Identity?.Name

api/QuestionsApi/Models/CreditModels.cs

@@ -36,7 +36,49 @@ public static class CreditEconomy
         Products.FirstOrDefault(value => value.Sku.Equals(sku, StringComparison.Ordinal));
 }
 
-public enum RzStoreGrant { ExamToken, QBankResetToken }
+public static class SlotMachineEconomy
+{
+    public const int SpinCost = 50;
+    public const int RollingSpinLimit = 200;
+    public static readonly TimeSpan SpinWindow = TimeSpan.FromHours(24);
+
+    public static readonly IReadOnlyList<SpinReward> Rewards =
+    [
+        new() { Key = "jackpot", Label = "10,000 RZ Coins", Description = "Jackpot!", Grant = RzStoreGrant.Coins, CoinAmount = 10000, Probability = 0.005 },
+        new() { Key = "epic", Label = "2,000 RZ Coins", Description = "Epic Reward", Grant = RzStoreGrant.Coins, CoinAmount = 2000, Probability = 0.02 },
+        new() { Key = "great", Label = "500 RZ Coins", Description = "Great Reward", Grant = RzStoreGrant.Coins, CoinAmount = 500, Probability = 0.10 },
+        new() { Key = "exam_token", Label = "Exam Simulation Token", Description = "Starts one new full exam simulation.", Grant = RzStoreGrant.ExamToken, Probability = 0.15 },
+        new() { Key = "qbank_reset", Label = "QBank Reset Token", Description = "Makes every QBank question eligible again.", Grant = RzStoreGrant.QBankResetToken, Probability = 0.20 },
+        new() { Key = "nice", Label = "100 RZ Coins", Description = "Nice!", Grant = RzStoreGrant.Coins, CoinAmount = 100, Probability = 0.30 },
+        new() { Key = "good_luck", Label = "50 RZ Coins", Description = "Good luck!", Grant = RzStoreGrant.Coins, CoinAmount = 50, Probability = 0.225 },
+    ];
+
+    public static SpinReward RollReward(double roll)
+    {
+        var cumulative = 0.0;
+        foreach (var reward in Rewards)
+        {
+            cumulative += reward.Probability;
+            if (roll < cumulative) return reward;
+        }
+        return Rewards[^1];
+    }
+
+    public static SpinReward? FindReward(string key) =>
+        Rewards.FirstOrDefault(value => value.Key.Equals(key, StringComparison.Ordinal));
+}
+
+public enum RzStoreGrant { ExamToken, QBankResetToken, Coins }
+
+public sealed class SpinReward
+{
+    public string Key { get; set; } = "";
+    public string Label { get; set; } = "";
+    public string Description { get; set; } = "";
+    public RzStoreGrant Grant { get; set; }
+    public int CoinAmount { get; set; }
+    public double Probability { get; set; }
+}
 
 public sealed class RzStoreProduct
 {
@@ -61,6 +103,14 @@ public sealed class CreditPurchaseEvent
     public DateTime CreatedUtc { get; set; }
 }
 
+public sealed class SpinEvent
+{
+    public string OperationId { get; set; } = "";
+    public string RewardKey { get; set; } = "";
+    public int CoinsWon { get; set; }
+    public DateTime CreatedUtc { get; set; }
+}
+
 public sealed class UserCreditAccount
 {
     [BsonId]
@@ -74,6 +124,8 @@ public sealed class UserCreditAccount
     public bool InitialExamGrantApplied { get; set; }
     public List<CreditEvent> RecentEarnings { get; set; } = [];
     public List<CreditPurchaseEvent> Purchases { get; set; } = [];
+    public List<SpinEvent> Spins { get; set; } = [];
+    public List<CreditEvent> RecentSpins { get; set; } = [];
     public List<string> AppliedOperations { get; set; } = [];
     public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
 }
@@ -102,10 +154,30 @@ public sealed class QBankResetRequest
     public string OperationId { get; set; } = "";
 }
 
-public enum CreditOperationResult { Succeeded, InsufficientCredits, InsufficientTokens, OperationConflict }
+public sealed class SpinRequest
+{
+    public string OperationId { get; set; } = "";
+}
+
+public enum CreditOperationResult { Succeeded, InsufficientCredits, InsufficientTokens, OperationConflict, RateLimited }
 
 public sealed class CreditOperationResponse
 {
     public CreditOperationResult Result { get; set; }
     public CreditStatusResponse Status { get; set; } = new();
 }
+
+public sealed class SpinConfigResponse
+{
+    public int SpinCost { get; set; } = SlotMachineEconomy.SpinCost;
+    public IReadOnlyList<SpinReward> Rewards { get; set; } = SlotMachineEconomy.Rewards;
+}
+
+public sealed class SpinResponse
+{
+    public CreditOperationResult Result { get; set; }
+    public string RewardKey { get; set; } = "";
+    public string RewardLabel { get; set; } = "";
+    public int CoinsWon { get; set; }
+    public CreditStatusResponse Status { get; set; } = new();
+}

api/QuestionsApi/Services/CreditStore.cs

@@ -130,6 +130,65 @@ public sealed class CreditStore
         return Response(CreditOperationResult.InsufficientTokens, account);
     }
 
+    public async Task<SpinResponse> SpinAsync(string userId, string operationId)
+    {
+        var now = _clock.GetUtcNow().UtcDateTime;
+        await EnsureAndCleanAsync(userId, now);
+        var existing = await _accounts.Find(value => value.UserId == userId).FirstAsync();
+        var priorSpin = existing.Spins.FirstOrDefault(value => value.OperationId == operationId);
+        if (priorSpin is not null)
+            return SpinResult(CreditOperationResult.Succeeded, existing, priorSpin);
+
+        var reward = SlotMachineEconomy.RollReward(Random.Shared.NextDouble());
+        var netCreditDelta = reward.Grant == RzStoreGrant.Coins
+            ? reward.CoinAmount - SlotMachineEconomy.SpinCost
+            : -SlotMachineEconomy.SpinCost;
+        var spinEvent = new SpinEvent
+        {
+            OperationId = operationId,
+            RewardKey = reward.Key,
+            CoinsWon = reward.Grant == RzStoreGrant.Coins ? reward.CoinAmount : 0,
+            CreatedUtc = now
+        };
+
+        var belowSpinCap = new BsonDocumentFilterDefinition<UserCreditAccount>(
+            new BsonDocument("$expr", new BsonDocument("$lt", new BsonArray
+            {
+                new BsonDocument("$size", new BsonDocument("$ifNull", new BsonArray { "$RecentSpins", new BsonArray() })),
+                SlotMachineEconomy.RollingSpinLimit
+            })));
+        var filter = Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
+            Builders<UserCreditAccount>.Filter.Gte(value => value.Credits, SlotMachineEconomy.SpinCost) &
+            Builders<UserCreditAccount>.Filter.Not(
+                Builders<UserCreditAccount>.Filter.ElemMatch(
+                    value => value.Spins, spin => spin.OperationId == operationId)) &
+            belowSpinCap;
+        var update = Builders<UserCreditAccount>.Update
+            .Inc(value => value.Credits, netCreditDelta)
+            .Push(value => value.Spins, spinEvent)
+            .Push(value => value.RecentSpins, new CreditEvent { OperationId = operationId, CreatedUtc = now })
+            .Set(value => value.UpdatedUtc, now);
+        update = reward.Grant switch
+        {
+            RzStoreGrant.ExamToken => update.Inc(value => value.ExamTokens, 1),
+            RzStoreGrant.QBankResetToken => update.Inc(value => value.QBankResetTokens, 1),
+            _ => update
+        };
+        var account = await _accounts.FindOneAndUpdateAsync(
+            filter, update, new FindOneAndUpdateOptions<UserCreditAccount>
+            {
+                ReturnDocument = ReturnDocument.After
+            });
+        if (account is not null) return SpinResult(CreditOperationResult.Succeeded, account, spinEvent);
+
+        account = await _accounts.Find(value => value.UserId == userId).FirstAsync();
+        priorSpin = account.Spins.FirstOrDefault(value => value.OperationId == operationId);
+        if (priorSpin is not null) return SpinResult(CreditOperationResult.Succeeded, account, priorSpin);
+        if (account.Credits < SlotMachineEconomy.SpinCost)
+            return SpinResult(CreditOperationResult.InsufficientCredits, account, null);
+        return SpinResult(CreditOperationResult.RateLimited, account, null);
+    }
+
     public async Task<bool> TryConsumeExamTokenAsync(string userId, string operationId)
     {
         var now = _clock.GetUtcNow().UtcDateTime;
@@ -166,6 +225,8 @@ public sealed class CreditStore
                 .SetOnInsert(value => value.InitialExamGrantApplied, true)
                 .SetOnInsert(value => value.RecentEarnings, [])
                 .SetOnInsert(value => value.Purchases, [])
+                .SetOnInsert(value => value.Spins, [])
+                .SetOnInsert(value => value.RecentSpins, [])
                 .SetOnInsert(value => value.AppliedOperations, [])
                 .SetOnInsert(value => value.UpdatedUtc, now),
             new UpdateOptions { IsUpsert = true });
@@ -183,6 +244,14 @@ public sealed class CreditStore
             Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
             Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.Purchases), false),
             Builders<UserCreditAccount>.Update.Set(value => value.Purchases, []));
+        await _accounts.UpdateOneAsync(
+            Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
+            Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.Spins), false),
+            Builders<UserCreditAccount>.Update.Set(value => value.Spins, []));
+        await _accounts.UpdateOneAsync(
+            Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
+            Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.RecentSpins), false),
+            Builders<UserCreditAccount>.Update.Set(value => value.RecentSpins, []));
         await _accounts.UpdateOneAsync(
             Builders<UserCreditAccount>.Filter.Eq(value => value.UserId, userId) &
             Builders<UserCreditAccount>.Filter.Exists(nameof(UserCreditAccount.AppliedOperations), false),
@@ -193,6 +262,12 @@ public sealed class CreditStore
             Builders<UserCreditAccount>.Update.PullFilter(
                 value => value.RecentEarnings,
                 earning => earning.CreatedUtc <= cutoff));
+        var spinCutoff = now - SlotMachineEconomy.SpinWindow;
+        await _accounts.UpdateOneAsync(
+            value => value.UserId == userId,
+            Builders<UserCreditAccount>.Update.PullFilter(
+                value => value.RecentSpins,
+                spin => spin.CreatedUtc <= spinCutoff));
     }
 
     private static CreditStatusResponse ToStatus(UserCreditAccount account) => new()
@@ -212,4 +287,14 @@ public sealed class CreditStore
             Result = result,
             Status = ToStatus(account)
         };
+
+    private static SpinResponse SpinResult(
+        CreditOperationResult result, UserCreditAccount account, SpinEvent? spinEvent) => new()
+        {
+            Result = result,
+            RewardKey = spinEvent?.RewardKey ?? "",
+            RewardLabel = spinEvent is null ? "" : SlotMachineEconomy.FindReward(spinEvent.RewardKey)?.Label ?? "",
+            CoinsWon = spinEvent?.CoinsWon ?? 0,
+            Status = ToStatus(account)
+        };
 }

scripts/autoload/credits_service.gd

@@ -3,6 +3,8 @@ extends Node
 signal credits_changed
 signal credits_failed(message: String)
 signal store_operation_completed(message: String)
+signal spin_resolved(reward_key: String, reward_label: String, coins_won: int)
+signal spin_config_loaded
 
 const EndpointConfig := preload("res://scripts/autoload/api_endpoint_config.gd")
 const DEFAULT_URL := "https://us3q.ranaze.com/api/credits"
@@ -12,10 +14,13 @@ var exam_tokens: int = 0
 var qbank_reset_tokens: int = 0
 var bank_cycle: int = 0
 var products: Array = []
+var spin_cost := 50
+var spin_rewards: Array = []
 var loaded := false
 var loading := false
 var request: HTTPRequest
 var action_request: HTTPRequest
+var spin_config_request: HTTPRequest
 var request_token := ""
 var api_url := DEFAULT_URL
 var pending_store_action := ""
@@ -33,6 +38,10 @@ func _ready() -> void:
 	action_request.timeout = 20.0
 	action_request.request_completed.connect(_on_action_completed)
 	add_child(action_request)
+	spin_config_request = HTTPRequest.new()
+	spin_config_request.timeout = 20.0
+	spin_config_request.request_completed.connect(_on_spin_config_completed)
+	add_child(spin_config_request)
 	AuthState.auth_changed.connect(_on_auth_changed)
 
 
@@ -83,8 +92,33 @@ func reset_qbank() -> void:
 	_post("/qbank-reset", {"confirmation": "RESET_QBANK", "operationId": _operation_id("reset")})
 
 
+func spin() -> void:
+	pending_store_action = "spin"
+	_post("/spin", {"operationId": _operation_id("spin")})
+
+
+func fetch_spin_config() -> void:
+	if not AuthState.can_send_authenticated_request():
+		return
+	var headers := PackedStringArray(["Authorization: Bearer %s" % AuthState.access_token])
+	spin_config_request.request(api_url + "/spin-config", headers, HTTPClient.METHOD_GET)
+
+
+func _on_spin_config_completed(result: int, response_code: int, _headers: PackedStringArray, body: PackedByteArray) -> void:
+	if result != HTTPRequest.RESULT_SUCCESS or response_code < 200 or response_code >= 300:
+		return
+	var parsed: Variant = JSON.parse_string(body.get_string_from_utf8())
+	if typeof(parsed) != TYPE_DICTIONARY:
+		return
+	spin_cost = int(parsed.get("spinCost", spin_cost))
+	spin_rewards = parsed.get("rewards", spin_rewards)
+	spin_config_loaded.emit()
+
+
 func _post(path: String, payload: Dictionary) -> void:
 	if not AuthState.can_send_authenticated_request():
+		pending_store_action = ""
+		credits_failed.emit("You're signed out. Sign back in and try again.")
 		return
 	var headers := PackedStringArray([
 		"Authorization: Bearer %s" % AuthState.access_token,
@@ -101,6 +135,16 @@ func _on_action_completed(result: int, response_code: int, _headers: PackedStrin
 		credits_failed.emit("The Rz Coin Store could not complete that action.")
 		return
 	if response_code >= 200 and response_code < 300 and typeof(parsed) == TYPE_DICTIONARY:
+		if pending_store_action == "spin":
+			var status: Variant = parsed.get("status", {})
+			if typeof(status) == TYPE_DICTIONARY:
+				apply_status(status)
+			pending_store_action = ""
+			spin_resolved.emit(
+				str(parsed.get("rewardKey", "")),
+				str(parsed.get("rewardLabel", "")),
+				int(parsed.get("coinsWon", 0)))
+			return
 		apply_status(parsed)
 		if pending_store_action == "reset":
 			ProfileService.reset_qbank_eligibility()
@@ -118,7 +162,7 @@ func _on_action_completed(result: int, response_code: int, _headers: PackedStrin
 
 
 func _operation_id(prefix: String) -> String:
-	return "%s:%s:%d" % [prefix, str(AuthState.user_id), Time.get_ticks_usec()]
+	return "%s:%s:%d" % [prefix, str(AuthState.username), Time.get_ticks_usec()]
 
 
 func _on_auth_changed() -> void:
@@ -128,6 +172,7 @@ func _on_auth_changed() -> void:
 		qbank_reset_tokens = 0
 		bank_cycle = 0
 		products = []
+		spin_rewards = []
 		loaded = false
 		loading = false
 		if request.get_http_client_status() != HTTPClient.STATUS_DISCONNECTED:

scripts/ui/main.gd

@@ -361,6 +361,11 @@ func _build_ui() -> void:
 	rz_store.main = self
 	screens_container.add_child(rz_store)
 	screens["rz_store"] = rz_store
+	var slot_machine := preload("res://scripts/ui/rz_slot_machine_screen.gd").new()
+	slot_machine.name = "RzSlotMachine"
+	slot_machine.main = self
+	screens_container.add_child(slot_machine)
+	screens["slot_machine"] = slot_machine
 
 	feedback_dialog = preload("res://scripts/ui/app_feedback_dialog.gd").new()
 	feedback_dialog.name = "AppFeedbackDialog"

scripts/ui/navigation_routes.gd

@@ -31,4 +31,6 @@ static func key_for_screen(screen_name: String, payload: Variant = null) -> Stri
 		key = "donations"
 	elif screen_name == "rz_store":
 		key = "rz_store"
+	elif screen_name == "slot_machine":
+		key = "rz_store"
 	return key

scripts/ui/rz_slot_machine_screen.gd

@@ -0,0 +1,517 @@
+extends VBoxContainer
+
+const Brand := preload("res://scripts/ui/medmind_style.gd")
+const STAR_ICON := preload("res://assets/icons/lucide/star.svg")
+const SHIELD_ICON := preload("res://assets/icons/lucide/shield.svg")
+const CLOCK_ICON := preload("res://assets/icons/lucide/clock-3.svg")
+const RESET_ICON := preload("res://assets/icons/lucide/rotate-ccw.svg")
+const REEL_SYMBOLS := [STAR_ICON, SHIELD_ICON, CLOCK_ICON, RESET_ICON]
+const ICON_BY_REWARD_KEY := {
+	"jackpot": "star",
+	"epic": "star",
+	"great": "star",
+	"exam_token": "clock-3",
+	"qbank_reset": "rotate-ccw",
+	"nice": "star",
+	"good_luck": "star",
+}
+
+var main: Control
+
+var subtitle_label: Label
+var back_button: Button
+var machine_panel: PanelContainer
+var reel_icons: Array = []
+var win_up_to_label: Label
+var cost_value_label: Label
+var spin_button: Button
+var auto_spin_toggle: CheckButton
+var status_label: Label
+var rewards_list: VBoxContainer
+var footer_card: PanelContainer
+var footer_icon_panel: PanelContainer
+var footer_icon: TextureRect
+var footer_heading: Label
+var footer_description: Label
+
+var _spinning := false
+
+
+func _ready() -> void:
+	size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	size_flags_vertical = Control.SIZE_EXPAND_FILL
+	add_theme_constant_override("separation", 18)
+
+	_build_header()
+
+	var body := HBoxContainer.new()
+	body.add_theme_constant_override("separation", 18)
+	body.size_flags_vertical = Control.SIZE_EXPAND_FILL
+	add_child(body)
+
+	_build_machine(body)
+	_build_rewards_panel(body)
+
+	status_label = Label.new()
+	status_label.add_theme_font_override("font", Brand.font)
+	status_label.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
+	add_child(status_label)
+
+	_build_footer()
+
+	CreditsService.credits_changed.connect(_refresh_spin_button)
+	CreditsService.spin_config_loaded.connect(_refresh_rewards)
+	UIThemeService.theme_changed.connect(func(_dark: bool): _refresh_theme_controls())
+	_refresh_rewards()
+	_refresh_spin_button()
+
+
+func on_show(_payload: Variant = null) -> void:
+	CreditsService.refresh()
+	CreditsService.fetch_spin_config()
+	_refresh_rewards()
+	_refresh_spin_button()
+
+
+func _build_header() -> void:
+	back_button = Button.new()
+	back_button.text = "← Back to Shop"
+	back_button.add_theme_font_override("font", Brand.font)
+	back_button.flat = true
+	back_button.size_flags_horizontal = Control.SIZE_SHRINK_BEGIN
+	back_button.pressed.connect(func(): main.show_screen("rz_store"))
+	add_child(back_button)
+
+	var title := Label.new()
+	title.text = "RZ Coin Slot Machine"
+	title.add_theme_font_override("font", Brand.font)
+	title.add_theme_font_size_override("font_size", 30)
+	add_child(title)
+	subtitle_label = Label.new()
+	subtitle_label.text = "Test your luck and win exciting rewards!"
+	subtitle_label.add_theme_font_override("font", Brand.font)
+	subtitle_label.add_theme_font_size_override("font_size", 14)
+	subtitle_label.add_theme_color_override("font_color", Brand.muted_color(UIThemeService.is_dark_mode()))
+	add_child(subtitle_label)
+
+
+func _build_machine(parent: Control) -> void:
+	var dark := UIThemeService.is_dark_mode()
+	machine_panel = PanelContainer.new()
+	machine_panel.size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	machine_panel.add_theme_stylebox_override("panel", Brand.content_card_box(dark, true, Brand.ROYAL_BLUE))
+	parent.add_child(machine_panel)
+
+	var margin := MarginContainer.new()
+	margin.add_theme_constant_override("margin_left", 20)
+	margin.add_theme_constant_override("margin_right", 20)
+	margin.add_theme_constant_override("margin_top", 18)
+	margin.add_theme_constant_override("margin_bottom", 18)
+	machine_panel.add_child(margin)
+
+	var column := VBoxContainer.new()
+	column.add_theme_constant_override("separation", 14)
+	margin.add_child(column)
+
+	var reels_row := HBoxContainer.new()
+	reels_row.add_theme_constant_override("separation", 12)
+	reels_row.alignment = BoxContainer.ALIGNMENT_CENTER
+	column.add_child(reels_row)
+
+	reel_icons.clear()
+	for _i in range(3):
+		var reel_panel := PanelContainer.new()
+		reel_panel.custom_minimum_size = Vector2(84, 84)
+		reel_panel.add_theme_stylebox_override("panel", Brand.icon_circle_box(dark, Brand.ROYAL_BLUE, 12))
+		var icon := TextureRect.new()
+		icon.texture = STAR_ICON
+		icon.modulate = Brand.AMBER
+		icon.custom_minimum_size = Vector2(40, 40)
+		icon.expand_mode = TextureRect.EXPAND_IGNORE_SIZE
+		icon.stretch_mode = TextureRect.STRETCH_KEEP_ASPECT_CENTERED
+		icon.size_flags_horizontal = Control.SIZE_SHRINK_CENTER
+		icon.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+		reel_panel.add_child(icon)
+		reels_row.add_child(reel_panel)
+		reel_icons.append(icon)
+
+	win_up_to_label = Label.new()
+	win_up_to_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
+	win_up_to_label.add_theme_font_override("font", Brand.font)
+	win_up_to_label.add_theme_font_size_override("font_size", 15)
+	win_up_to_label.add_theme_color_override("font_color", Brand.text_color(dark))
+	column.add_child(win_up_to_label)
+
+	var controls_row := HBoxContainer.new()
+	controls_row.add_theme_constant_override("separation", 14)
+	column.add_child(controls_row)
+
+	var cost_box := VBoxContainer.new()
+	cost_box.add_theme_constant_override("separation", 0)
+	var cost_caption := Label.new()
+	cost_caption.text = "Cost per spin"
+	cost_caption.add_theme_font_override("font", Brand.font)
+	cost_caption.add_theme_font_size_override("font_size", 11)
+	cost_caption.add_theme_color_override("font_color", Brand.muted_color(dark))
+	cost_box.add_child(cost_caption)
+	cost_value_label = Label.new()
+	cost_value_label.add_theme_font_override("font", Brand.font)
+	cost_value_label.add_theme_font_size_override("font_size", 15)
+	cost_value_label.add_theme_color_override("font_color", Brand.text_color(dark))
+	cost_box.add_child(cost_value_label)
+	controls_row.add_child(cost_box)
+
+	spin_button = Button.new()
+	spin_button.text = "Spin"
+	spin_button.custom_minimum_size = Vector2(120, 44)
+	spin_button.size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	spin_button.add_theme_font_override("font", Brand.font)
+	_style_spin_button()
+	spin_button.pressed.connect(_on_spin_pressed)
+	controls_row.add_child(spin_button)
+
+	var auto_box := VBoxContainer.new()
+	auto_box.add_theme_constant_override("separation", 0)
+	auto_spin_toggle = CheckButton.new()
+	auto_spin_toggle.text = "Auto Spin"
+	auto_spin_toggle.add_theme_font_override("font", Brand.font)
+	auto_box.add_child(auto_spin_toggle)
+	var auto_caption := Label.new()
+	auto_caption.text = "10 spins"
+	auto_caption.add_theme_font_override("font", Brand.font)
+	auto_caption.add_theme_font_size_override("font_size", 11)
+	auto_caption.add_theme_color_override("font_color", Brand.muted_color(dark))
+	auto_box.add_child(auto_caption)
+	controls_row.add_child(auto_box)
+
+	var info_label := Label.new()
+	info_label.text = "All rewards are instant and sent to your account."
+	info_label.add_theme_font_override("font", Brand.font)
+	info_label.add_theme_font_size_override("font_size", 11)
+	info_label.add_theme_color_override("font_color", Brand.muted_color(dark))
+	info_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
+	column.add_child(info_label)
+
+
+func _build_rewards_panel(parent: Control) -> void:
+	var dark := UIThemeService.is_dark_mode()
+	var panel := PanelContainer.new()
+	panel.custom_minimum_size = Vector2(280, 0)
+	panel.add_theme_stylebox_override("panel", Brand.content_card_box(dark, false))
+	parent.add_child(panel)
+
+	var margin := MarginContainer.new()
+	margin.add_theme_constant_override("margin_left", 16)
+	margin.add_theme_constant_override("margin_right", 16)
+	margin.add_theme_constant_override("margin_top", 14)
+	margin.add_theme_constant_override("margin_bottom", 14)
+	panel.add_child(margin)
+
+	var column := VBoxContainer.new()
+	column.add_theme_constant_override("separation", 10)
+	margin.add_child(column)
+
+	var heading := Label.new()
+	heading.text = "Possible Rewards"
+	heading.add_theme_font_override("font", Brand.font)
+	heading.add_theme_font_size_override("font_size", 16)
+	heading.add_theme_color_override("font_color", Brand.text_color(dark))
+	column.add_child(heading)
+
+	rewards_list = VBoxContainer.new()
+	rewards_list.add_theme_constant_override("separation", 10)
+	column.add_child(rewards_list)
+
+
+func _build_footer() -> void:
+	var dark := UIThemeService.is_dark_mode()
+	footer_card = PanelContainer.new()
+	footer_card.add_theme_stylebox_override("panel", Brand.content_card_box(dark, false))
+	add_child(footer_card)
+
+	var margin := MarginContainer.new()
+	margin.add_theme_constant_override("margin_left", 16)
+	margin.add_theme_constant_override("margin_right", 16)
+	margin.add_theme_constant_override("margin_top", 12)
+	margin.add_theme_constant_override("margin_bottom", 12)
+	footer_card.add_child(margin)
+
+	var row := HBoxContainer.new()
+	row.add_theme_constant_override("separation", 14)
+	margin.add_child(row)
+
+	footer_icon_panel = PanelContainer.new()
+	footer_icon_panel.custom_minimum_size = Vector2(36, 36)
+	footer_icon_panel.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+	footer_icon_panel.add_theme_stylebox_override("panel", Brand.icon_circle_box(dark, Brand.ROYAL_BLUE, 18))
+	footer_icon = TextureRect.new()
+	footer_icon.texture = STAR_ICON
+	footer_icon.custom_minimum_size = Vector2(18, 18)
+	footer_icon.expand_mode = TextureRect.EXPAND_IGNORE_SIZE
+	footer_icon.stretch_mode = TextureRect.STRETCH_KEEP_ASPECT_CENTERED
+	footer_icon.modulate = Brand.ROYAL_BLUE
+	footer_icon_panel.add_child(footer_icon)
+	row.add_child(footer_icon_panel)
+
+	var copy := VBoxContainer.new()
+	copy.size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	copy.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+	copy.add_theme_constant_override("separation", 2)
+	footer_heading = Label.new()
+	footer_heading.text = "How it works"
+	footer_heading.add_theme_font_override("font", Brand.font)
+	footer_heading.add_theme_font_size_override("font_size", 15)
+	footer_heading.add_theme_color_override("font_color", Brand.text_color(dark))
+	copy.add_child(footer_heading)
+	footer_description = Label.new()
+	footer_description.text = "Spend RZ Coins to spin the slot machine. Win coins, boosts, tokens, and more!"
+	footer_description.add_theme_font_override("font", Brand.font)
+	footer_description.add_theme_font_size_override("font_size", 12)
+	footer_description.add_theme_color_override("font_color", Brand.muted_color(dark))
+	footer_description.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
+	copy.add_child(footer_description)
+	row.add_child(copy)
+
+
+func _refresh_theme_controls() -> void:
+	var dark := UIThemeService.is_dark_mode()
+	subtitle_label.add_theme_color_override("font_color", Brand.muted_color(dark))
+	machine_panel.add_theme_stylebox_override("panel", Brand.content_card_box(dark, true, Brand.ROYAL_BLUE))
+	win_up_to_label.add_theme_color_override("font_color", Brand.text_color(dark))
+	cost_value_label.add_theme_color_override("font_color", Brand.text_color(dark))
+	footer_card.add_theme_stylebox_override("panel", Brand.content_card_box(dark, false))
+	footer_icon_panel.add_theme_stylebox_override("panel", Brand.icon_circle_box(dark, Brand.ROYAL_BLUE, 18))
+	footer_heading.add_theme_color_override("font_color", Brand.text_color(dark))
+	footer_description.add_theme_color_override("font_color", Brand.muted_color(dark))
+	_refresh_rewards()
+
+
+func _reward_color(key: String) -> Color:
+	match key:
+		"jackpot": return Brand.AMBER
+		"epic": return Brand.PURPLE
+		"great": return Brand.ROYAL_BLUE
+		"exam_token": return Brand.ROYAL_BLUE
+		"qbank_reset": return Brand.SUCCESS
+		"nice": return Brand.SKY_BLUE
+		"good_luck": return Brand.SLATE
+		_: return Brand.ROYAL_BLUE
+
+
+func _refresh_rewards() -> void:
+	var dark := UIThemeService.is_dark_mode()
+	cost_value_label.text = "%d RZ Coins" % CreditsService.spin_cost
+
+	var max_coins := 0
+	for reward_variant in CreditsService.spin_rewards:
+		if typeof(reward_variant) != TYPE_DICTIONARY:
+			continue
+		max_coins = maxi(max_coins, int((reward_variant as Dictionary).get("coinAmount", 0)))
+	win_up_to_label.text = "Win up to %s RZ Coins!" % _format_thousands(max_coins) if max_coins > 0 else ""
+
+	for child in rewards_list.get_children():
+		child.queue_free()
+	for reward_variant in CreditsService.spin_rewards:
+		if typeof(reward_variant) != TYPE_DICTIONARY:
+			continue
+		var reward: Dictionary = reward_variant
+		rewards_list.add_child(_build_reward_row(dark, reward))
+
+
+func _build_reward_row(dark: bool, reward: Dictionary) -> HBoxContainer:
+	var key := str(reward.get("key", ""))
+	var accent := _reward_color(key)
+	var row := HBoxContainer.new()
+	row.add_theme_constant_override("separation", 10)
+
+	var icon_panel := PanelContainer.new()
+	icon_panel.custom_minimum_size = Vector2(32, 32)
+	icon_panel.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+	icon_panel.add_theme_stylebox_override("panel", Brand.icon_circle_box(dark, accent, 16))
+	var icon := TextureRect.new()
+	icon.texture = load("res://assets/icons/lucide/%s.svg" % str(ICON_BY_REWARD_KEY.get(key, "star")))
+	icon.custom_minimum_size = Vector2(16, 16)
+	icon.expand_mode = TextureRect.EXPAND_IGNORE_SIZE
+	icon.stretch_mode = TextureRect.STRETCH_KEEP_ASPECT_CENTERED
+	icon.modulate = accent
+	icon_panel.add_child(icon)
+	row.add_child(icon_panel)
+
+	var copy := VBoxContainer.new()
+	copy.size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	copy.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+	copy.add_theme_constant_override("separation", 0)
+	var label := Label.new()
+	label.text = str(reward.get("label", ""))
+	label.add_theme_font_override("font", Brand.font)
+	label.add_theme_font_size_override("font_size", 13)
+	label.add_theme_color_override("font_color", Brand.text_color(dark))
+	copy.add_child(label)
+	var description := Label.new()
+	description.text = str(reward.get("description", ""))
+	description.add_theme_font_override("font", Brand.font)
+	description.add_theme_font_size_override("font_size", 11)
+	description.add_theme_color_override("font_color", Brand.muted_color(dark))
+	copy.add_child(description)
+	row.add_child(copy)
+
+	var percent_label := Label.new()
+	percent_label.text = "%s%%" % _format_percent(float(reward.get("probability", 0.0)) * 100.0)
+	percent_label.add_theme_font_override("font", Brand.font)
+	percent_label.add_theme_font_size_override("font_size", 13)
+	percent_label.add_theme_color_override("font_color", accent)
+	row.add_child(percent_label)
+
+	return row
+
+
+func _refresh_spin_button() -> void:
+	spin_button.disabled = _spinning or CreditsService.credits < CreditsService.spin_cost
+
+
+func _on_spin_pressed() -> void:
+	if _spinning:
+		return
+	_spinning = true
+	_refresh_spin_button()
+	var spin_count := 10 if auto_spin_toggle.button_pressed else 1
+	for _i in range(spin_count):
+		if CreditsService.credits < CreditsService.spin_cost:
+			break
+		var should_continue := await _do_one_spin()
+		if not should_continue:
+			break
+	_spinning = false
+	_refresh_spin_button()
+
+
+func _do_one_spin() -> bool:
+	_animate_reels()
+	var result := await _await_spin_result()
+	if not result.get("ok", false):
+		status_label.text = str(result.get("message", "The spin could not be completed."))
+		status_label.add_theme_color_override("font_color", Brand.MAGENTA)
+		return false
+
+	var reward_label := str(result.get("reward_label", ""))
+	var coins_won := int(result.get("coins_won", 0))
+	status_label.text = "You won: %s" % reward_label
+	status_label.add_theme_color_override("font_color", Brand.SUCCESS)
+	if coins_won > 0:
+		_play_coin_burst(coins_won)
+	elif main != null:
+		var credits_badge: Object = main.get("credits_badge")
+		if credits_badge != null:
+			credits_badge.bump()
+	return true
+
+
+func _await_spin_result() -> Dictionary:
+	var result := {}
+	var on_resolved := func(reward_key: String, reward_label: String, coins_won: int):
+		result.merge({"ok": true, "reward_key": reward_key, "reward_label": reward_label, "coins_won": coins_won}, true)
+	var on_failed := func(message: String):
+		result.merge({"ok": false, "message": message}, true)
+	CreditsService.spin_resolved.connect(on_resolved, CONNECT_ONE_SHOT)
+	CreditsService.credits_failed.connect(on_failed, CONNECT_ONE_SHOT)
+	CreditsService.spin()
+	var deadline := Time.get_ticks_msec() + 20000
+	while result.is_empty() and Time.get_ticks_msec() < deadline:
+		await get_tree().process_frame
+	if result.is_empty():
+		result = {"ok": false, "message": "The spin timed out. Check your connection and try again."}
+	if CreditsService.spin_resolved.is_connected(on_resolved):
+		CreditsService.spin_resolved.disconnect(on_resolved)
+	if CreditsService.credits_failed.is_connected(on_failed):
+		CreditsService.credits_failed.disconnect(on_failed)
+	return result
+
+
+func _animate_reels() -> void:
+	for index in range(reel_icons.size()):
+		_spin_one_reel(reel_icons[index], 0.9 + index * 0.25)
+
+
+func _spin_one_reel(icon: TextureRect, duration: float) -> void:
+	var elapsed := 0.0
+	var interval := 0.06
+	while elapsed < duration:
+		icon.texture = REEL_SYMBOLS[randi() % REEL_SYMBOLS.size()]
+		await get_tree().create_timer(interval).timeout
+		elapsed += interval
+		interval = minf(interval * 1.18, 0.22)
+	icon.texture = STAR_ICON
+	icon.modulate = Brand.AMBER
+
+
+func _play_coin_burst(coins_won: int) -> void:
+	if main == null:
+		return
+	var credits_badge: Control = main.get("credits_badge")
+	if credits_badge == null or not is_instance_valid(credits_badge):
+		return
+	var origin := machine_panel.get_global_rect().get_center()
+	var target := credits_badge.get_global_rect().get_center()
+	var coin_count := clampi(3 + coins_won / 500, 4, 10)
+	var flight_time := 0.55
+	var stagger := 0.035
+	for index in range(coin_count):
+		var coin := TextureRect.new()
+		coin.texture = STAR_ICON
+		coin.modulate = Brand.AMBER
+		coin.custom_minimum_size = Vector2(16, 16)
+		coin.size = Vector2(16, 16)
+		coin.top_level = true
+		coin.mouse_filter = Control.MOUSE_FILTER_IGNORE
+		coin.pivot_offset = Vector2(8, 8)
+		var jitter := Vector2(randf_range(-24.0, 24.0), randf_range(-16.0, 16.0))
+		coin.global_position = origin + jitter - coin.size * 0.5
+		add_child(coin)
+		var tween := create_tween()
+		tween.tween_interval(index * stagger)
+		tween.set_parallel(true)
+		tween.tween_property(coin, "global_position", target - coin.size * 0.5, flight_time).set_trans(Tween.TRANS_CUBIC).set_ease(Tween.EASE_IN)
+		tween.tween_property(coin, "scale", Vector2(0.6, 0.6), flight_time).set_trans(Tween.TRANS_CUBIC).set_ease(Tween.EASE_IN)
+		tween.set_parallel(false)
+		tween.tween_callback(coin.queue_free)
+	var settle_time := (coin_count - 1) * stagger + flight_time
+	get_tree().create_timer(settle_time).timeout.connect(func():
+		if is_instance_valid(credits_badge):
+			credits_badge.bump())
+
+
+func _style_spin_button() -> void:
+	var normal := StyleBoxFlat.new()
+	normal.bg_color = Brand.ROYAL_BLUE
+	normal.set_corner_radius_all(8)
+	var hover := StyleBoxFlat.new()
+	hover.bg_color = Brand.SKY_BLUE
+	hover.set_corner_radius_all(8)
+	var disabled := StyleBoxFlat.new()
+	disabled.bg_color = Color(Brand.ROYAL_BLUE, 0.35)
+	disabled.set_corner_radius_all(8)
+	spin_button.add_theme_stylebox_override("normal", normal)
+	spin_button.add_theme_stylebox_override("hover", hover)
+	spin_button.add_theme_stylebox_override("pressed", normal)
+	spin_button.add_theme_stylebox_override("disabled", disabled)
+	spin_button.add_theme_color_override("font_color", Brand.DARK_TEXT)
+	spin_button.add_theme_color_override("font_hover_color", Brand.DARK_TEXT)
+	spin_button.add_theme_color_override("font_disabled_color", Color(Brand.DARK_TEXT, 0.7))
+
+
+func _format_thousands(value: int) -> String:
+	var digits := str(absi(value))
+	var grouped := ""
+	var count := 0
+	for index in range(digits.length() - 1, -1, -1):
+		grouped = digits[index] + grouped
+		count += 1
+		if count % 3 == 0 and index != 0:
+			grouped = "," + grouped
+	return ("-" if value < 0 else "") + grouped
+
+
+func _format_percent(value: float) -> String:
+	if absf(value - roundf(value)) < 0.001:
+		return str(int(roundf(value)))
+	return "%.1f" % value

scripts/ui/rz_store_screen.gd

@@ -28,6 +28,10 @@ var balance_value_label: Label
 var coin_caption_label: Label
 var inventory_label: Label
 var tab_controls: Array = []
+var banner_card: PanelContainer
+var banner_icon_panel: PanelContainer
+var banner_heading: Label
+var banner_description: Label
 var section_heading: Label
 var section_subtitle: Label
 var products_grid: HFlowContainer
@@ -49,6 +53,7 @@ func _ready() -> void:
 	_build_header()
 	_build_summary_card()
 	_build_tabs()
+	_build_slot_machine_banner()
 
 	section_heading = Label.new()
 	section_heading.text = "Featured"
@@ -217,6 +222,63 @@ func _apply_tab_theme(dark: bool) -> void:
 		(entry["underline"] as ColorRect).color = Brand.ROYAL_BLUE if active else Color(0, 0, 0, 0)
 
 
+func _build_slot_machine_banner() -> void:
+	var dark := UIThemeService.is_dark_mode()
+	banner_card = PanelContainer.new()
+	banner_card.add_theme_stylebox_override("panel", Brand.content_card_box(dark, true, Brand.ROYAL_BLUE))
+	add_child(banner_card)
+
+	var margin := MarginContainer.new()
+	margin.add_theme_constant_override("margin_left", 16)
+	margin.add_theme_constant_override("margin_right", 16)
+	margin.add_theme_constant_override("margin_top", 12)
+	margin.add_theme_constant_override("margin_bottom", 12)
+	banner_card.add_child(margin)
+
+	var row := HBoxContainer.new()
+	row.add_theme_constant_override("separation", 14)
+	margin.add_child(row)
+
+	banner_icon_panel = PanelContainer.new()
+	banner_icon_panel.custom_minimum_size = Vector2(40, 40)
+	banner_icon_panel.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+	banner_icon_panel.add_theme_stylebox_override("panel", Brand.icon_circle_box(dark, Brand.ROYAL_BLUE, 20))
+	var icon := TextureRect.new()
+	icon.texture = load("res://assets/icons/lucide/star.svg")
+	icon.custom_minimum_size = Vector2(20, 20)
+	icon.expand_mode = TextureRect.EXPAND_IGNORE_SIZE
+	icon.stretch_mode = TextureRect.STRETCH_KEEP_ASPECT_CENTERED
+	icon.modulate = Brand.ROYAL_BLUE
+	banner_icon_panel.add_child(icon)
+	row.add_child(banner_icon_panel)
+
+	var copy := VBoxContainer.new()
+	copy.size_flags_horizontal = Control.SIZE_EXPAND_FILL
+	copy.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+	copy.add_theme_constant_override("separation", 2)
+	banner_heading = Label.new()
+	banner_heading.text = "RZ Coin Slot Machine"
+	banner_heading.add_theme_font_override("font", Brand.font)
+	banner_heading.add_theme_font_size_override("font_size", 15)
+	banner_heading.add_theme_color_override("font_color", Brand.text_color(dark))
+	copy.add_child(banner_heading)
+	banner_description = Label.new()
+	banner_description.text = "Spend RZ Coins for a chance at bigger rewards."
+	banner_description.add_theme_font_override("font", Brand.font)
+	banner_description.add_theme_font_size_override("font_size", 12)
+	banner_description.add_theme_color_override("font_color", Brand.muted_color(dark))
+	copy.add_child(banner_description)
+	row.add_child(copy)
+
+	var play_button := Button.new()
+	play_button.text = "Play Now"
+	play_button.custom_minimum_size = Vector2(96, 36)
+	play_button.add_theme_font_override("font", Brand.font)
+	_style_buy_button(play_button)
+	play_button.pressed.connect(func(): main.show_screen("slot_machine"))
+	row.add_child(play_button)
+
+
 func _build_footer() -> void:
 	var dark := UIThemeService.is_dark_mode()
 	footer_card = PanelContainer.new()
@@ -276,6 +338,10 @@ func _refresh_theme_controls() -> void:
 	coin_caption_label.add_theme_color_override("font_color", Brand.muted_color(dark))
 	inventory_label.add_theme_color_override("font_color", Brand.muted_color(dark))
 	_apply_tab_theme(dark)
+	banner_card.add_theme_stylebox_override("panel", Brand.content_card_box(dark, true, Brand.ROYAL_BLUE))
+	banner_icon_panel.add_theme_stylebox_override("panel", Brand.icon_circle_box(dark, Brand.ROYAL_BLUE, 20))
+	banner_heading.add_theme_color_override("font_color", Brand.text_color(dark))
+	banner_description.add_theme_color_override("font_color", Brand.muted_color(dark))
 	section_subtitle.add_theme_color_override("font_color", Brand.muted_color(dark))
 	footer_card.add_theme_stylebox_override("panel", Brand.content_card_box(dark, false))
 	footer_icon_panel.add_theme_stylebox_override("panel", Brand.icon_circle_box(dark, Brand.ROYAL_BLUE, 18))