Reveal the flashcard answer by tapping the card, not a separate button

Matches the mockup: the "Show Answer" button is replaced by an in-card
"Tap card to reveal answer" hint, and clicking anywhere on the card
reveals it (guarded the same way Space already was - only while at the
live card and not yet revealed).

scripts/ui/flashcards_study.gd

@@ -55,7 +55,7 @@ var back_label: Label
 var extra_caption: Label
 var extra_label: Label
 var card_position_label: Label
-var reveal_button: Button
+var tap_hint_label: Label
 var grade_row: HBoxContainer
 var grade_buttons: Dictionary = {}
 var undo_button: Button
@@ -184,6 +184,8 @@ func _build() -> void:
 	card_panel = PanelContainer.new()
 	card_panel.custom_minimum_size = Vector2(720, 420)
 	card_panel.add_theme_stylebox_override("panel", Brand.content_card_box(UIThemeService.is_dark_mode(), true, Brand.ROYAL_BLUE))
+	card_panel.mouse_filter = Control.MOUSE_FILTER_STOP
+	card_panel.gui_input.connect(_on_card_panel_input)
 	center.add_child(card_panel)
 	var card_content := VBoxContainer.new()
 	card_content.add_theme_constant_override("separation", 20)
@@ -206,6 +208,13 @@ func _build() -> void:
 	divider.visible = false
 	card_content.add_child(divider)
 
+	var tap_hint_center := CenterContainer.new()
+	card_content.add_child(tap_hint_center)
+	tap_hint_label = Label.new()
+	tap_hint_label.text = "Tap card to reveal answer"
+	tap_hint_label.visible = false
+	tap_hint_center.add_child(tap_hint_label)
+
 	var answer_block := VBoxContainer.new()
 	answer_block.add_theme_constant_override("separation", 4)
 	card_content.add_child(answer_block)
@@ -240,13 +249,6 @@ func _build() -> void:
 	card_position_label.visible = false
 	position_row.add_child(card_position_label)
 
-	reveal_button = Button.new()
-	reveal_button.text = "Show Answer  (Space)"
-	reveal_button.custom_minimum_size = Vector2(0, 52)
-	_style_gradient_button(reveal_button)
-	reveal_button.pressed.connect(_reveal)
-	center_column.add_child(reveal_button)
-
 	grade_row = HBoxContainer.new()
 	grade_row.add_theme_constant_override("separation", 10)
 	grade_row.visible = false
@@ -309,14 +311,6 @@ func _caption_label(text: String) -> Label:
 	return label
 
 
-func _style_gradient_button(button: Button) -> void:
-	button.add_theme_stylebox_override("normal", Brand.gradient_button_box())
-	button.add_theme_stylebox_override("hover", Brand.gradient_button_box())
-	button.add_theme_stylebox_override("pressed", Brand.gradient_button_box())
-	button.add_theme_color_override("font_color", Color.WHITE)
-	button.add_theme_color_override("font_hover_color", Color.WHITE)
-
-
 func _style_ghost_button(button: Button, dark: bool) -> void:
 	var empty := StyleBoxEmpty.new()
 	button.add_theme_stylebox_override("normal", empty)
@@ -565,6 +559,7 @@ func refresh_theme_controls() -> void:
 	extra_caption.add_theme_color_override("font_color", Brand.muted_color(dark))
 	extra_label.add_theme_color_override("font_color", Brand.muted_color(dark))
 	card_position_label.add_theme_color_override("font_color", Brand.muted_color(dark))
+	tap_hint_label.add_theme_color_override("font_color", Brand.muted_color(dark))
 	_style_ghost_button(undo_button, dark)
 	previous_button.add_theme_stylebox_override("normal", Brand.secondary_button_box(dark))
 	previous_button.add_theme_stylebox_override("hover", Brand.secondary_button_box(dark, true))
@@ -706,7 +701,7 @@ func _render_history_entry(index: int) -> void:
 	_render_card()
 	_reveal()
 	grade_row.visible = false
-	reveal_button.visible = false
+	tap_hint_label.visible = false
 	var is_graded_entry: bool = entry.get("action", "") == "graded"
 	var is_last_graded_card: bool = str(entry.get("card_id", "")) == last_card_id
 	var has_undoable_review: bool = not last_client_review_id.is_empty()
@@ -811,7 +806,7 @@ func _render_loading() -> void:
 	front_label.visible = true
 	front_label.text = "Loading..."
 	_hide_answer()
-	reveal_button.visible = false
+	tap_hint_label.visible = false
 	grade_row.visible = false
 
 
@@ -819,7 +814,7 @@ func _render_empty(card: Dictionary) -> void:
 	empty_label.visible = true
 	front_label.visible = false
 	_hide_answer()
-	reveal_button.visible = false
+	tap_hint_label.visible = false
 	grade_row.visible = false
 	progress_label.text = "0 due"
 	if typeof(card) == TYPE_DICTIONARY:
@@ -844,7 +839,8 @@ func _render_card() -> void:
 		front_label.text = str(current_note.get("prompt", ""))
 	front_label.visible = true
 	_hide_answer()
-	reveal_button.visible = true
+	divider.visible = true
+	tap_hint_label.visible = true
 	grade_row.visible = false
 	progress_label.text = "%d due, %d new available" % [due_remaining, new_remaining]
 
@@ -866,13 +862,20 @@ func _reveal() -> void:
 	extra_caption.visible = not extra.is_empty()
 	extra_label.visible = not extra.is_empty()
 	extra_label.text = extra
-	reveal_button.visible = false
+	tap_hint_label.visible = false
 	grade_row.visible = true
 	for rating in grade_buttons:
 		var button: Button = grade_buttons[rating]
 		button.text = "%s\n%s" % [rating.capitalize(), _interval_label_for(rating)]
 
 
+func _on_card_panel_input(event: InputEvent) -> void:
+	if history_cursor != session_history.size() or revealed:
+		return
+	if event is InputEventMouseButton and event.pressed and event.button_index == MOUSE_BUTTON_LEFT:
+		_reveal()
+
+
 func _interval_label_for(rating: String) -> String:
 	for option in rating_options:
 		if str(option.get("rating", "")) == rating:

tests/flashcard_session_navigation_test.gd

@@ -135,8 +135,8 @@ func _run() -> void:
 	screen._go_next()
 	_assert(screen.front_label.text == "P3(live)" and screen.history_cursor == screen.session_history.size(),
 		"stepping past the last history entry should return to the live card")
-	_assert(screen.reveal_button.visible and not screen.grade_row.visible,
-		"returning to a live, unrevealed card should restore the reveal prompt")
+	_assert(screen.tap_hint_label.visible and not screen.grade_row.visible,
+		"returning to a live, unrevealed card should restore the tap-to-reveal hint")
 
 	screen._go_next()
 	_assert(screen.session_history.size() == 3 and screen.session_history[2]["action"] == "skipped" and screen.session_history[2]["card_id"] == "card-3",

tests/flashcard_study_render_test.gd

@@ -29,7 +29,7 @@ func _initialize() -> void:
 	]
 	screen._render_card()
 	_assert(screen.front_label.text == "2 + 2 = ?", "the front should show only the prompt before reveal")
-	_assert(screen.reveal_button.visible, "the reveal button should be visible before the answer is shown")
+	_assert(screen.tap_hint_label.visible, "the tap-to-reveal hint should be visible before the answer is shown")
 	_assert(not screen.grade_row.visible, "grading buttons should be hidden before reveal")
 	_assert(not screen.back_label.visible, "the back should stay hidden before reveal")
 
@@ -38,7 +38,7 @@ func _initialize() -> void:
 	_assert(screen.extra_label.text == "Basic arithmetic" and screen.extra_label.visible, "the extra takeaway should render in its own labeled section")
 	_assert(screen.answer_caption.visible and screen.extra_caption.visible, "revealing a card with an extra should show both the answer and takeaway captions")
 	_assert(screen.grade_row.visible, "grading buttons should appear after reveal")
-	_assert(not screen.reveal_button.visible, "the reveal button should hide once the card is revealed")
+	_assert(not screen.tap_hint_label.visible, "the tap-to-reveal hint should hide once the card is revealed")
 	_assert(screen.grade_buttons["good"].text.contains("1d"), "each grade button should show its computed next interval")
 
 	# Cloze card: only the card's own variant is hidden on the front; back reveals everything.
@@ -60,6 +60,23 @@ func _initialize() -> void:
 	screen._reveal()
 	_assert(not screen.extra_label.visible and not screen.extra_caption.visible, "a card with no extra takeaway should hide that section instead of showing an empty caption")
 
+	# Tapping the card panel reveals the answer, same as pressing Space.
+	screen.current_note = {"type": "basic", "prompt": "Tap test", "answer": "Tapped", "extra": ""}
+	screen.current_card = {"id": "card-4", "variant": 0, "revision": 1}
+	screen.revealed = false
+	screen._render_card()
+	var click := InputEventMouseButton.new()
+	click.button_index = MOUSE_BUTTON_LEFT
+	click.pressed = true
+	screen._on_card_panel_input(click)
+	_assert(screen.revealed and screen.back_label.text == "Tapped", "clicking the card panel should reveal the answer")
+
+	# A second tap after reveal (or while browsing history) is a no-op - it must not re-trigger
+	# any reveal side effects (grading is guarded elsewhere; this only checks idempotence).
+	screen.back_label.text = "Tapped"
+	screen._on_card_panel_input(click)
+	_assert(screen.back_label.text == "Tapped", "tapping an already-revealed card should be a no-op")
+
 	screen.free()
 	quit(1 if failures > 0 else 0)