Restructure into themed screens with flag card backs, real font, flip animation and sound

- Replace the bogus DroidSansJapanese.ttf (an HTML page) with M PLUS Rounded 1c,
  loaded with LoadFontEx and explicit kana codepoints
- Theme struct per language with flag-based card backs (Hinomaru, Taegukgi, Trairong)
- Card art rendered to textures so the flip squashes the whole card
- Synthesized flip/match/mismatch/win/click sounds (new audio package)
- Shared ui package for text and buttons; Screen enum replaces i32 ids
- Kana <-> romaji pairs drawn from all 46 basic hiragana

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/themes/themes.odin

@@ -2,40 +2,91 @@ package themes
 
 import raylib "vendor:raylib"
 
-SCREEN_WIDTH: i32 = 1280
-SCREEN_HEIGHT: i32 = 720
+SCREEN_WIDTH  :: 1280
+SCREEN_HEIGHT :: 720
 
-JAPAN_PRIMARY: raylib.Color = raylib.Color{230, 57, 70, 255}
-JAPAN_ACCENT: raylib.Color = raylib.Color{253, 184, 190, 255}
-JAPAN_BACKGROUND: raylib.Color = raylib.Color{250, 245, 245, 255}
-KOREA_PRIMARY: raylib.Color = raylib.Color{0, 71, 160, 255}
-KOREA_ACCENT: raylib.Color = raylib.Color{180, 180, 255, 255}
-KOREA_BACKGROUND: raylib.Color = raylib.Color{245, 248, 255, 255}
-THAI_PRIMARY: raylib.Color = raylib.Color{165, 25, 49, 255}
-THAI_ACCENT: raylib.Color = raylib.Color{255, 180, 200, 255}
-THAI_BACKGROUND: raylib.Color = raylib.Color{255, 245, 248, 255}
-WHITE: raylib.Color = raylib.Color{255, 255, 255, 255}
-BLACK: raylib.Color = raylib.Color{0, 0, 0, 255}
-DARK_GRAY: raylib.Color = raylib.Color{64, 64, 64, 255}
-LIGHT_GRAY: raylib.Color = raylib.Color{200, 200, 200, 255}
-CARD_BACK_COLOR: raylib.Color = raylib.Color{40, 40, 50, 255}
+Screen :: enum {
+    MAIN_MENU,
+    JAPANESE_MENU,
+    JAPANESE_MEMORY,
+    KOREAN_MENU,
+    THAI_MENU,
+}
 
-BUTTON_WIDTH: i32 = 240
-BUTTON_HEIGHT: i32 = 60
-TITLE_FONT_SIZE: i32 = 72
-SUBTITLE_FONT_SIZE: i32 = 24
-BUTTON_FONT_SIZE: i32 = 24
+// Which national flag the card backs are modelled on
+Flag :: enum {
+    JAPAN,    // Nisshōki / Hinomaru
+    KOREA,    // Taegukgi
+    THAILAND, // Thong Trairong
+}
 
-CARD_WIDTH: i32 = 90
-CARD_HEIGHT: i32 = 120
-CARD_SPACING: i32 = 12
-GRID_TOP: i32 = 140
-GRID_ROWS: i32 = 4
-GRID_COLS: i32 = 6
-FLIP_DELAY: f32 = 1.0
+Theme :: struct {
+    name:       cstring,
+    flag:       Flag,
+    primary:    raylib.Color, // main brand color (buttons, titles)
+    secondary:  raylib.Color, // second flag color
+    accent:     raylib.Color, // highlights, matched outlines
+    background: raylib.Color,
+    card_face:  raylib.Color,
+    ink:        raylib.Color, // body text
+}
 
-MAIN_MENU: i32 = 0
-JAPANESE_SCREEN: i32 = 1
-JAPANESE_MEMORY: i32 = 2
-KOREAN_SCREEN: i32 = 3
-THAI_SCREEN: i32 = 4
+// Flag colors
+HINOMARU_RED :: raylib.Color{188, 0, 45, 255}
+TAEGUK_RED   :: raylib.Color{205, 46, 58, 255}
+TAEGUK_BLUE  :: raylib.Color{0, 71, 160, 255}
+THAI_RED     :: raylib.Color{165, 25, 49, 255}
+THAI_BLUE    :: raylib.Color{45, 42, 74, 255}
+
+WHITE      :: raylib.Color{255, 255, 255, 255}
+BLACK      :: raylib.Color{0, 0, 0, 255}
+SUMI_INK   :: raylib.Color{35, 31, 32, 255}
+DARK_GRAY  :: raylib.Color{80, 76, 72, 255}
+LIGHT_GRAY :: raylib.Color{200, 200, 200, 255}
+MENU_BACKGROUND :: raylib.Color{248, 246, 242, 255}
+
+JAPAN :: Theme{
+    name       = "Japanese",
+    flag       = .JAPAN,
+    primary    = HINOMARU_RED,
+    secondary  = WHITE,
+    accent     = raylib.Color{212, 160, 23, 255}, // kin (gold)
+    background = raylib.Color{250, 246, 238, 255}, // washi paper
+    card_face  = raylib.Color{255, 252, 245, 255},
+    ink        = SUMI_INK,
+}
+
+KOREA :: Theme{
+    name       = "Korean",
+    flag       = .KOREA,
+    primary    = TAEGUK_BLUE,
+    secondary  = TAEGUK_RED,
+    accent     = raylib.Color{30, 30, 30, 255}, // trigram black
+    background = raylib.Color{244, 246, 251, 255},
+    card_face  = raylib.Color{255, 255, 255, 255},
+    ink        = raylib.Color{22, 24, 35, 255},
+}
+
+THAI :: Theme{
+    name       = "Thai",
+    flag       = .THAILAND,
+    primary    = THAI_RED,
+    secondary  = THAI_BLUE,
+    accent     = raylib.Color{218, 165, 32, 255}, // temple gold
+    background = raylib.Color{251, 246, 240, 255},
+    card_face  = raylib.Color{255, 253, 248, 255},
+    ink        = raylib.Color{30, 28, 45, 255},
+}
+
+BUTTON_WIDTH  :: 240
+BUTTON_HEIGHT :: 60
+TITLE_FONT_SIZE    :: 72
+SUBTITLE_FONT_SIZE :: 26
+BUTTON_FONT_SIZE   :: 26
+
+CARD_WIDTH   :: 96
+CARD_HEIGHT  :: 128
+CARD_SPACING :: 14
+GRID_TOP     :: 136
+GRID_ROWS    :: 4
+GRID_COLS    :: 6