/* ===== Theme (pixel art) — matches connect-4 ===== */
:root {
  --bg: #1a1c2c;
  --panel: #29366f;
  --panel-2: #333c57;
  --border: #0b0b14;
  --ink: #f4f4f4;
  --muted: #94b0c2;
  --accent: #41a6f6;
  --accent-dark: #3b5dc9;
  --radius: 0px;
  --font-pixel: "Press Start 2P", "Courier New", monospace;
  --font-term: "VT323", "Courier New", monospace;
  --pixel-shadow: 4px 4px 0 #000;
  --pixel-shadow-lg: 6px 6px 0 #000;

  /* 2048 tile colors */
  --tile-2: #6bb2e5;
  --tile-2-dark: #4a7fa8;
  --tile-2-text: #1a1c2c;
  --tile-4: #2089d5;
  --tile-4-dark: #16629b;
  --tile-4-text: #f4f4f4;
  --tile-8: #1c557d;
  --tile-8-dark: #123a58;
  --tile-8-text: #f4f4f4;
  --tile-16: #ffd93d;
  --tile-16-dark: #b8982a;
  --tile-16-text: #1a1c2c;
  --tile-32: #ffc300;
  --tile-32-dark: #b38900;
  --tile-32-text: #1a1c2c;
  --tile-64: #ff9900;
  --tile-64-dark: #b36b00;
  --tile-64-text: #1a1c2c;
  --tile-128: #ff6b00;
  --tile-128-dark: #b34b00;
  --tile-128-text: #1a1c2c;
  --tile-256: #f53d2e;
  --tile-256-dark: #ad2a20;
  --tile-256-text: #f4f4f4;
  --tile-512: #d91e18;
  --tile-512-dark: #981511;
  --tile-512-text: #f4f4f4;
  --tile-1024: #a80f0a;
  --tile-1024-dark: #760a07;
  --tile-1024-text: #f4f4f4;
  --tile-2048: #6e0b05;
  --tile-2048-dark: #4c0804;
  --tile-2048-text: #f4f4f4;
  --tile-super: #ffcd75;
  --tile-super-dark: #c98f2b;
  --tile-super-text: #1a1c2c;

  /* Board material — same retro language as connect-4. */
  --board-frame: #11131f;
  --cell-empty: #11131f;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  /* Kill pull-to-refresh while letting normal scrolling work.
     Must be on html too: when content overflows, html is the real
     scrolling element and body-only rules don't stop the refresh. */
  overscroll-behavior-y: none;
}

body {
  font-family: var(--font-term);
  background: var(--bg);
  color: var(--ink);
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100dvh;
  padding-bottom: 16px;
  image-rendering: pixelated;
  /* Prevent pull-to-refresh / rubber-band overscroll on touch devices. */
  overscroll-behavior-y: none;
  touch-action: manipulation;
}

/* ===== Header ===== */
.site-header {
  text-align: center;
  padding: 20px 16px 8px;
}

.title {
  margin: 0;
  font-family: var(--font-pixel);
  font-size: clamp(18px, 4vw, 26px);
  letter-spacing: 1px;
  font-weight: 400;
  text-transform: uppercase;
  color: var(--ink);
  text-shadow: 3px 3px 0 #000;
}

/* The title is a link back to the games hub — keep the exact title look. */
.title-link {
  color: inherit;
  text-decoration: none;
}

.subtitle {
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 20px;
  letter-spacing: 1px;
}

/* ===== Layout ===== */
.container {
  width: 100%;
  max-width: 860px;
  padding: 16px;
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
}

/* ===== Score Bar ===== */
.score-bar {
  display: flex;
  gap: 16px;
  margin-bottom: 16px;
  width: 100%;
  max-width: 500px;
}

.score-box {
  flex: 1;
  background: var(--panel);
  border: 4px solid #000;
  border-radius: var(--radius);
  box-shadow: var(--pixel-shadow-lg);
  padding: 12px 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.score-label {
  font-family: var(--font-pixel);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--muted);
}

.score-value {
  font-family: var(--font-pixel);
  font-size: clamp(16px, 4vw, 22px);
  color: var(--ink);
  text-shadow: 2px 2px 0 #000;
}

/* ===== Board ===== */
.board-wrap {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  background: var(--panel);
  border: 4px solid #000;
  border-radius: var(--radius);
  box-shadow: var(--pixel-shadow-lg);
  padding: 18px;
  width: 100%;
  max-width: 500px;
}

/* Retro CRT scanlines over the board (purely visual, never blocks input). */
.board-wrap::after {
  content: "";
  position: absolute;
  inset: 0;
  background: repeating-linear-gradient(
    to bottom,
    rgba(0, 0, 0, 0.07) 0px,
    rgba(0, 0, 0, 0.07) 1px,
    transparent 1px,
    transparent 3px
  );
  pointer-events: none;
  z-index: 1000;
}

.board {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  grid-template-rows: repeat(4, minmax(0, 1fr));
  gap: 12px;
  background: var(--panel);
  border: 6px solid var(--board-frame);
  border-radius: var(--radius);
  padding: 12px;
  width: 100%;
  aspect-ratio: 1 / 1;
  position: relative;
  image-rendering: pixelated;
  /* Swipes on the board are game input only: the browser must never
     interpret them as scroll or pull-to-refresh. */
  touch-action: none;
}

/* Baby mode: 5x5 grid. Tracks use minmax(0, 1fr) like the 4x4 board so tile
   content (e.g. the wide "1024" text) can NEVER stretch the cells — squares
   always stay exactly the same size in both modes. Gap/padding are slimmer
   than 4x4 so the smaller cells get as much room as possible. */
.board-5 {
  grid-template-columns: repeat(5, minmax(0, 1fr));
  grid-template-rows: repeat(5, minmax(0, 1fr));
  gap: 8px;
  padding: 10px;
  border-width: 5px;
}

/* Baby mode board panel: larger than the 4x4 one (the .board-5 class lives on
   the inner .board, reached via :has) and with slimmer padding. */
.board-wrap:has(.board-5) {
  max-width: 644px; /* 15% bigger than the 560px board */
  padding: 14px;
}

/* ===== Tiles ===== */
/* Base tile = empty slot: dark cavity, like the holes in the connect-4 board. */
.tile {
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius);
  border: 3px solid #000;
  background: var(--cell-empty);
  font-family: var(--font-pixel);
  font-size: clamp(14px, 3.5vw, 28px);
  font-weight: 400;
  text-shadow: 2px 2px 0 rgba(0, 0, 0, 0.3);
  transition: transform 0.12s steps(4);
  user-select: none;
  aspect-ratio: 1 / 1;
  /* Size container: lets the digit-count rules below scale the font to the
     tile's own width (cqw), so any number always fits its cell. */
  container-type: inline-size;
}

/* Digit-count font sizing (class added by app.js): min() picks the smaller of
   the viewport clamp and a cell-relative size (cqw), so the number always fits
   its tile. The pixel font runs slightly wider than 1em/char and casts a 2px
   shadow, so the cqw factors leave ~25% headroom (n chars ≈ n × cqw × 1.1). */
.tile.d1 {
  font-size: min(clamp(14px, 3.5vw, 28px), 55cqw);
}

.tile.d2 {
  font-size: min(clamp(14px, 3.5vw, 28px), 36cqw);
}

.tile.d3 {
  font-size: min(clamp(11px, 3.2vw, 26px), 24cqw);
}

.tile.d4 {
  font-size: min(clamp(9px, 2.6vw, 24px), 18cqw);
}

.tile.tile-new {
  animation: tile-appear 0.16s steps(4) forwards;
}

.tile.tile-merged {
  animation: tile-merge 0.22s steps(5) forwards;
  z-index: 10;
}

/* Filled tiles: solid pixel bevel, same formula as the connect-4 chips. */
.tile-2 {
  background: var(--tile-2);
  color: var(--tile-2-text);
  box-shadow: inset -5px -5px 0 var(--tile-2-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.25);
}

.tile-4 {
  background: var(--tile-4);
  color: var(--tile-4-text);
  box-shadow: inset -5px -5px 0 var(--tile-4-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.25);
}

.tile-8 {
  background: var(--tile-8);
  color: var(--tile-8-text);
  box-shadow: inset -5px -5px 0 var(--tile-8-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.25);
}

.tile-16 {
  background: var(--tile-16);
  color: var(--tile-16-text);
  box-shadow: inset -5px -5px 0 var(--tile-16-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.3);
}

.tile-32 {
  background: var(--tile-32);
  color: var(--tile-32-text);
  box-shadow: inset -5px -5px 0 var(--tile-32-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.3);
}

.tile-64 {
  background: var(--tile-64);
  color: var(--tile-64-text);
  box-shadow: inset -5px -5px 0 var(--tile-64-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.3);
}

.tile-128 {
  background: var(--tile-128);
  color: var(--tile-128-text);
  box-shadow: inset -5px -5px 0 var(--tile-128-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.3);
}

.tile-256 {
  background: var(--tile-256);
  color: var(--tile-256-text);
  box-shadow: inset -5px -5px 0 var(--tile-256-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.25);
}

.tile-512 {
  background: var(--tile-512);
  color: var(--tile-512-text);
  box-shadow: inset -5px -5px 0 var(--tile-512-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.25);
}

.tile-1024 {
  background: var(--tile-1024);
  color: var(--tile-1024-text);
  box-shadow: inset -5px -5px 0 var(--tile-1024-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.25);
}

.tile-2048 {
  background: var(--tile-2048);
  color: var(--tile-2048-text);
  box-shadow: inset -5px -5px 0 var(--tile-2048-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.25);
  animation: tile-glow 1.5s ease-in-out infinite alternate;
}

.tile-super {
  background: var(--tile-super);
  color: var(--tile-super-text);
  box-shadow: inset -5px -5px 0 var(--tile-super-dark),
    inset 4px 4px 0 rgba(255, 255, 255, 0.3);
}

/* Tile animations */
@keyframes tile-appear {
  0% {
    transform: scale(0);
    opacity: 0;
  }
  50% {
    transform: scale(1.1);
  }
  100% {
    transform: scale(1);
    opacity: 1;
  }
}

@keyframes tile-pop {
  0% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.15);
  }
  100% {
    transform: scale(1);
  }
}

/* Highlight for tiles that just merged: a big pulse + bright white flash so
   the player instantly sees which two tiles combined. Uses filter (not
   box-shadow) so each tile keeps its own solid pixel bevel while glowing. */
@keyframes tile-merge {
  0% {
    transform: scale(1);
    filter: drop-shadow(0 0 0 rgba(255, 255, 255, 0.9));
  }
  40% {
    transform: scale(1.25);
    filter: drop-shadow(0 0 12px rgba(255, 255, 255, 0.75));
  }
  100% {
    transform: scale(1);
    filter: drop-shadow(0 0 0 rgba(255, 255, 255, 0));
  }
}

@keyframes tile-glow {
  0% {
    box-shadow: inset -5px -5px 0 var(--tile-2048-dark),
      inset 4px 4px 0 rgba(255, 255, 255, 0.25),
      0 0 10px rgba(255, 205, 117, 0.5);
  }
  100% {
    box-shadow: inset -5px -5px 0 var(--tile-2048-dark),
      inset 4px 4px 0 rgba(255, 255, 255, 0.25),
      0 0 20px rgba(255, 205, 117, 0.8);
  }
}

/* ===== Minecraft-style merge particles ===== */
/* Small squares in the merged tile's color that burst outward, fall with
   gravity and vanish — like breaking a block. Direction/distance come from
   --dx/--dy1/--dy2 set per particle in JS; steps() keeps the motion chunky. */
.particle {
  position: absolute;
  border: 2px solid #000;
  z-index: 1001; /* above the CRT scanline overlay */
  pointer-events: none;
  image-rendering: pixelated;
  animation: particle-burst 0.45s steps(5, end) forwards;
}

@keyframes particle-burst {
  0% {
    transform: translate(0, 0) scale(1);
    opacity: 1;
  }
  55% {
    transform: translate(calc(var(--dx) * 0.7), var(--dy1)) scale(1);
    opacity: 1;
  }
  100% {
    transform: translate(var(--dx), var(--dy2)) scale(0.7);
    opacity: 0;
  }
}

/* ===== Game Message Overlay ===== */
.game-message {
  display: none;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(26, 28, 44, 0.85);
  border: 6px solid #000;
  border-radius: var(--radius);
  z-index: 100;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 20px;
  animation: fade-in 0.15s steps(2) forwards;
}

.game-message.active {
  display: flex;
}

@keyframes fade-in {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

.game-message p {
  font-family: var(--font-pixel);
  font-size: clamp(18px, 4vw, 28px);
  color: var(--ink);
  text-shadow: 3px 3px 0 #000;
  text-align: center;
  margin: 0;
}

.message-buttons {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  justify-content: center;
}

/* ===== Game Bar ===== */
.game-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 16px;
  width: 100%;
  max-width: 500px;
}

.hint {
  font-family: var(--font-term);
  font-size: 16px;
  color: var(--muted);
  letter-spacing: 1px;
  margin: 0;
}

.key-hint {
  font-family: var(--font-pixel);
  font-size: 10px;
  background: var(--panel-2);
  border: 2px solid #000;
  padding: 4px 8px;
  box-shadow: 2px 2px 0 #000;
  display: inline-block;
}

/* ===== Mode picker (Normal 4x4 / Baby 5x5) ===== */
.mode-pick {
  display: flex;
  gap: 8px;
}

.btn-pick {
  font-family: var(--font-pixel);
  font-size: 10px;
  border: 3px solid #000;
  border-radius: 0;
  background: var(--panel-2);
  color: var(--ink);
  padding: 8px 12px;
  cursor: pointer;
  box-shadow: 3px 3px 0 #000;
  transition: transform 0.08s steps(2), box-shadow 0.08s steps(2);
}

.btn-pick:active {
  transform: translate(3px, 3px);
  box-shadow: 0 0 0 #000;
}

.btn-pick.active {
  background: var(--accent);
  color: #fff;
}

.controls-hint {
  text-align: center;
  margin: 14px 0 0;
  width: 100%;
  max-width: 500px;
}

/* ===== Buttons ===== */
.btn {
  font-family: var(--font-pixel);
  font-size: 11px;
  border: 3px solid #000;
  border-radius: 0;
  padding: 10px 14px;
  font-weight: 400;
  cursor: pointer;
  box-shadow: var(--pixel-shadow);
  transition: transform 0.08s steps(2), box-shadow 0.08s steps(2),
    background 0.08s steps(2);
}

.btn:hover {
  background: #283252;
}

.btn:active {
  transform: translate(4px, 4px);
  box-shadow: 0 0 0 #000;
}

.btn-ghost {
  background: var(--panel-2);
  color: var(--ink);
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}

.btn-primary:hover {
  background: var(--accent-dark);
}

.hidden {
  display: none !important;
}

/* ===== Bottom Link ===== */
.bottom-link {
  display: flex;
  justify-content: center;
  margin-top: 32px;
}

.bottom-link a {
  text-decoration: none;
}

/* ===== Responsive ===== */
@media (max-width: 520px) {
  .board {
    gap: 8px;
    padding: 8px;
  }

  .tile {
    font-size: clamp(10px, 3vw, 18px);
    border-width: 2px;
  }

  .score-bar {
    gap: 10px;
  }

  .score-box {
    padding: 10px 12px;
  }

  .score-label {
    font-size: 8px;
  }

  .score-value {
    font-size: clamp(14px, 3.5vw, 18px);
  }

  .game-bar {
    flex-direction: column;
    gap: 10px;
  }

  .btn-pick {
    font-size: 8px;
    padding: 7px 10px;
  }

  .title {
    font-size: 16px;
  }

  .hint {
    font-size: 14px;
  }
}