:root {
  --radius: clamp(4px, 1.2vw, 8px);
  --bg: #eef2f6;
  --ink: #2c3e50;
  --ink-soft: #607281;
  --board-bg: #34495e;
  --cell-bg: rgba(255, 255, 255, 0.08);
  --overlay-bg: rgba(238, 242, 246, 0.85);
  --surface: #dde6ee;
  --accent: #587894;
  --accent-dark: #34506b;
  --link-color: #34506b;
  --tile-card-bg: #fdfefe;

  --tile-2-bg: #eef2f6;      --tile-2-fg: #2c3e50;
  --tile-4-bg: #dbe6ee;      --tile-4-fg: #2c3e50;
  --tile-8-bg: #7fb3d5;      --tile-8-fg: #fff;
  --tile-16-bg: #5b9bd5;     --tile-16-fg: #fff;
  --tile-32-bg: #4a7fb5;     --tile-32-fg: #fff;
  --tile-64-bg: #3a5f95;     --tile-64-fg: #fff;
  --tile-128-bg: #6fcf97;    --tile-128-fg: #fff;
  --tile-256-bg: #4bb87a;    --tile-256-fg: #fff;
  --tile-512-bg: #2f9c5f;    --tile-512-fg: #fff;
  --tile-1024-bg: #f2c94c;   --tile-1024-fg: #2c3e50;
  --tile-2048-bg: #f2994a;   --tile-2048-fg: #fff;
  --tile-super-bg: #eb5757;  --tile-super-fg: #fff;
}

* { box-sizing: border-box; }

/* Page-level rules (body background, font, scrolling) live in
   assets/site.css — the game only lays out inside .sf-stage, which is sized
   to exactly one screen below the site header. */
.app {
  width: 100%;
  max-width: 560px;
  height: 100%;
  max-height: 820px;
  padding: clamp(4px, 1.5vw, 12px) clamp(12px, 3vw, 24px) clamp(12px, 3vw, 24px);
  color: var(--ink);
  display: flex;
  flex-direction: column;
  gap: clamp(8px, 2.5vw, 16px);
}

.side-panel {
  display: contents;
}

.heading { order: 1; }
.above-game { order: 2; }
.board-wrap { order: 3; }
.footer { order: 4; }

.heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px 10px;
}

.title-block {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.title {
  margin: 0;
  line-height: 1;
  font-size: clamp(22px, 5.5vw, 30px);
  font-weight: 800;
  color: var(--ink);
  letter-spacing: 0.5px;
}

/* A standalone pill badge, not plain colored text sitting next to the
   title — explicit light text on a fixed accent fill keeps it readable in
   both themes regardless of --ink/--bg contrast, and reads as its own
   "hex tile" chip rather than a subtitle. */
.title-sub {
  display: inline-block;
  padding: 3px 10px;
  font-size: clamp(10px, 2.8vw, 13px);
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: #fff;
  background: var(--accent-dark);
  border-radius: 999px;
}

.scores-container {
  display: flex;
  gap: 8px;
}

.score-box {
  background: var(--accent);
  color: #fff;
  border-radius: var(--radius);
  padding: 4px 12px;
  min-width: 58px;
  text-align: center;
  display: flex;
  flex-direction: column;
  line-height: 1.15;
}

.score-label {
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  opacity: 0.85;
  letter-spacing: 0.5px;
}

.score-value {
  font-size: clamp(14px, 3.2vw, 18px);
  font-weight: 700;
}

.above-game {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px 10px;
}

.game-intro {
  margin: 0;
  font-size: clamp(12px, 3vw, 14px);
  color: var(--ink-soft);
  line-height: 1.4;
}

.game-actions {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
  max-width: 100%;
  margin-left: auto;
}

.btn-new-game,
.btn-undo {
  flex-shrink: 0;
  border: none;
  background: var(--accent-dark);
  color: #fff;
  font-weight: 700;
  font-size: clamp(12px, 3vw, 14px);
  padding: 10px 16px;
  border-radius: var(--radius);
  cursor: pointer;
  touch-action: manipulation;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.btn-new-game:active,
.btn-undo:active {
  background: var(--accent);
}

.btn-undo svg {
  width: 1.15em;
  height: 1.15em;
}

.btn-undo:disabled {
  opacity: 0.4;
  cursor: default;
  pointer-events: none;
}

.btn-theme-toggle {
  flex-shrink: 0;
  border: none;
  background: var(--surface);
  color: var(--ink);
  line-height: 1;
  width: clamp(34px, 8vw, 40px);
  height: clamp(34px, 8vw, 40px);
  border-radius: var(--radius);
  cursor: pointer;
  touch-action: manipulation;
  display: flex;
  align-items: center;
  justify-content: center;
}

.btn-theme-toggle svg {
  width: 55%;
  height: 55%;
}

.btn-theme-toggle .icon-moon {
  display: none;
}

:root[data-theme="dark"] .btn-theme-toggle .icon-sun {
  display: none;
}

:root[data-theme="dark"] .btn-theme-toggle .icon-moon {
  display: block;
}

.btn-theme-toggle:active {
  background: var(--cell-bg);
}

.board-wrap {
  width: 100%;
  flex: 1 1 auto;
  min-height: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* The hex board's own width/height (in px) is computed and set by
   measureBoard() in game.js from the cube-coordinate geometry — CSS just
   provides the visual chrome (background card + rounded corners). */
.board {
  position: relative;
  background: var(--board-bg);
  border-radius: calc(var(--radius) + 8px);
  overflow: hidden;
  touch-action: none;
  user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
}

.grid-bg,
.tile-layer {
  position: absolute;
  inset: 0;
}

/* Every hex cell/tile is a positioned box (left/top/width/height set by JS
   to the exact cube-coordinate bounding box for that cell) containing an
   inner element that's actually clipped to a flat-top hexagon and inset a
   few percent, so neighbouring hexagons show a visible gap between them
   without changing the layout math itself. */
.hex-cell,
.hex-tile {
  position: absolute;
}

.hex-shape {
  position: absolute;
  inset: 5%;
  clip-path: polygon(25% 0%, 75% 0%, 100% 50%, 75% 100%, 25% 100%, 0% 50%);
  display: flex;
  align-items: center;
  justify-content: center;
}

.hex-cell .hex-shape {
  background: var(--cell-bg);
}

.hex-tile .hex-shape {
  background: var(--tile-2-bg);
  color: var(--tile-2-fg);
  font-weight: 700;
  font-size: clamp(14px, 6vw, 32px);
  transition: background-color 100ms ease-in-out;
}

.hex-tile {
  transition: top 100ms ease-in-out, left 100ms ease-in-out;
  will-change: top, left;
}

.tile-layer.no-transition .hex-tile {
  transition: none;
}

.hex-tile[data-value="2"]    .hex-shape { background: var(--tile-2-bg);    color: var(--tile-2-fg); }
.hex-tile[data-value="4"]    .hex-shape { background: var(--tile-4-bg);    color: var(--tile-4-fg); }
.hex-tile[data-value="8"]    .hex-shape { background: var(--tile-8-bg);    color: var(--tile-8-fg); }
.hex-tile[data-value="16"]   .hex-shape { background: var(--tile-16-bg);   color: var(--tile-16-fg); }
.hex-tile[data-value="32"]   .hex-shape { background: var(--tile-32-bg);   color: var(--tile-32-fg); }
.hex-tile[data-value="64"]   .hex-shape { background: var(--tile-64-bg);   color: var(--tile-64-fg); }
.hex-tile[data-value="128"]  .hex-shape { background: var(--tile-128-bg);  color: var(--tile-128-fg); }
.hex-tile[data-value="256"]  .hex-shape { background: var(--tile-256-bg);  color: var(--tile-256-fg); }
.hex-tile[data-value="512"]  .hex-shape { background: var(--tile-512-bg);  color: var(--tile-512-fg); }
.hex-tile[data-value="1024"] .hex-shape { background: var(--tile-1024-bg); color: var(--tile-1024-fg); }
.hex-tile[data-value="2048"] .hex-shape { background: var(--tile-2048-bg); color: var(--tile-2048-fg); }
.hex-tile[data-super="true"] .hex-shape { background: var(--tile-super-bg); color: var(--tile-super-fg); }

.hex-tile.new .hex-shape {
  animation: pop 160ms ease-in-out;
}

.hex-tile.merged .hex-shape {
  animation: pop 140ms ease-in-out;
  z-index: 2;
}

@keyframes pop {
  0%   { transform: scale(0.4); }
  60%  { transform: scale(1.08); }
  100% { transform: scale(1); }
}

.overlay {
  position: absolute;
  inset: 0;
  background: var(--overlay-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
}

.overlay[hidden] { display: none; }

.overlay-box {
  text-align: center;
  padding: var(--overlay-box-padding, 16px);
  max-width: 100%;
  max-height: 100%;
  overflow: hidden;
}

.overlay-title {
  font-size: var(--overlay-title-size, clamp(22px, 6vw, 32px));
  font-weight: 800;
  margin: 0 0 var(--overlay-title-gap, 16px);
  color: var(--ink);
  line-height: 1.2;
}

.overlay-actions {
  display: flex;
  gap: var(--overlay-actions-gap, 10px);
  justify-content: center;
  flex-wrap: wrap;
}

.btn-overlay {
  border: none;
  border-radius: var(--radius);
  padding: var(--overlay-btn-padding, 10px 18px);
  font-weight: 700;
  font-size: var(--overlay-btn-size, clamp(13px, 3.4vw, 15px));
  cursor: pointer;
  touch-action: manipulation;
}

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

.btn-secondary {
  background: var(--surface);
  color: var(--ink);
}

.keymap {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 16px;
}

.keymap-row {
  display: flex;
  justify-content: center;
  gap: 8px;
}

.keycap {
  width: 64px;
  height: 64px;
  background: var(--surface);
  border-radius: var(--radius);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
}

.keycap-arrow {
  font-size: 20px;
  line-height: 1;
  color: var(--accent-dark);
}

.keycap-key {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.5px;
  color: var(--ink-soft);
}

.footer {
  text-align: center;
}

.attribution {
  margin: 0;
  font-size: clamp(11px, 2.8vw, 13px);
  color: var(--ink-soft);
}

.attribution a {
  color: var(--link-color);
  text-decoration: underline;
}

@media (max-height: 700px) {
  .app {
    gap: 4px;
    padding: 8px clamp(12px, 3vw, 24px);
  }
  .game-intro {
    display: none;
  }
  .title {
    font-size: clamp(20px, 6vw, 32px);
  }
  .score-box {
    padding: 3px 10px;
  }
  .btn-new-game,
  .btn-undo {
    padding: 6px 12px;
  }
  .footer {
    font-size: 10px;
  }
}

@media (max-height: 300px) {
  .footer {
    display: none;
  }
  .app {
    padding: 6px clamp(12px, 3vw, 24px);
    gap: 2px;
  }
  .title-sub {
    display: none;
  }
  .btn-new-game,
  .btn-undo {
    padding: 2px 10px;
    font-size: 11px;
  }
}

@media (max-width: 260px) {
  .btn-new-game,
  .btn-undo {
    padding: 6px 8px;
    font-size: 11px;
  }
  .btn-theme-toggle,
  .btn-info {
    width: 26px;
    height: 26px;
    font-size: 12px;
  }
  .game-actions {
    gap: 4px;
  }
}

@media (max-height: 220px) {
  .app {
    padding: 4px clamp(12px, 3vw, 24px);
    gap: 1px;
  }
  .title {
    font-size: 14px;
    letter-spacing: 0;
  }
  .score-box {
    padding: 1px 6px;
    min-width: 36px;
  }
  .score-label {
    font-size: 7px;
  }
  .score-value {
    font-size: 11px;
  }
  .btn-new-game,
  .btn-undo {
    padding: 1px 8px;
    font-size: 10px;
  }
  .btn-theme-toggle,
  .btn-info {
    width: 20px;
    height: 20px;
    font-size: 11px;
  }
}

:root[data-theme="dark"] {
  --bg: #161d24;
  --ink: #e7edf2;
  --ink-soft: #9fb0bd;
  --board-bg: #1c2833;
  --cell-bg: rgba(255, 255, 255, 0.05);
  --overlay-bg: rgba(22, 29, 36, 0.85);
  --surface: #26313c;
  --accent: #3d5a75;
  --accent-dark: #29405a;
  --link-color: #8fb8db;
}

/* The keyboard map now lives in the article below the game. */
.sf-article .keymap {
  margin: 8px 0 20px;
}

.sf-article .keycap {
  background: #e3ebf2;
  width: 72px;
  height: 72px;
}

.sf-article .keycap-arrow { color: #34506b; font-size: 22px; }
.sf-article .keycap-key { color: #2c3e50; font-size: 14px; }

:root[data-theme="dark"] .sf-article .keycap { background: #26313c; }
:root[data-theme="dark"] .sf-article .keycap-arrow { color: #8fb8db; }
:root[data-theme="dark"] .sf-article .keycap-key { color: #e7edf2; }