*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg: #faf8f0;
  --text: #776e65;
  --text-light: #b0a89e;
  --board-bg: #bbada0;
  --cell-bg: #cdc1b4;

  --tile-2: #eee4da;
  --tile-4: #ede0c8;
  --tile-8: #f2b179;
  --tile-16: #f59563;
  --tile-32: #f67c5f;
  --tile-64: #f65e3b;
  --tile-128: #edcf72;
  --tile-256: #edcc61;
  --tile-512: #edc850;
  --tile-1024: #edc53f;
  --tile-2048: #edc22e;
  --tile-4096: #3c3a32;
  --tile-8192: #4a2840;
  --tile-16384: #232a38;
  --tile-32768: #500f1c;
  --tile-65536: #0a1120;
  --tile-super: #1c1b18;

  --tile-text-dark: #776e65;
  --tile-text-light: #f9f6f2;

  --font-body: 'Space Grotesk', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  --board-size: min(350px, calc(100vh - 240px), calc(100vw - 32px));
  --cell-gap: 8px;
  --cell-size: calc((var(--board-size) - 5 * var(--cell-gap)) / 4);
  --radius: 6px;
}

html, body {
  height: 100vh;
  height: 100dvh;
  overflow: hidden;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
}

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 8px 16px 36px;
  -webkit-tap-highlight-color: transparent;
}

.container {
  width: 100%;
  max-width: var(--board-size);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  position: relative;
}

/* -- header -- */

.header {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.title {
  font-family: var(--font-mono);
  font-size: 2.3rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -1px;
}

.title-accent {
  color: var(--text-light);
  font-weight: 400;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 8px;
}

.latency-badge {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-light);
  background: rgba(187, 173, 160, 0.15);
  border: 1px solid var(--board-bg);
  padding: 5px 10px;
  border-radius: 14px;
  letter-spacing: 0.5px;
  user-select: none;
}

.btn-nerds {
  padding: 5px 11px;
  border: 1.5px solid var(--board-bg);
  border-radius: 14px;
  background: none;
  color: var(--text);
  font-family: var(--font-body);
  font-size: 0.72rem;
  font-weight: 600;
  cursor: pointer;
  letter-spacing: 0.2px;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}

.btn-nerds:hover {
  background: var(--board-bg);
  color: #fff;
}

.btn-icon {
  width: 32px;
  height: 32px;
  border: 1.5px solid var(--board-bg);
  border-radius: 50%;
  background: none;
  color: var(--text-light);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 700;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
  display: flex;
  align-items: center;
  justify-content: center;
}

.btn-icon:hover {
  color: var(--text);
  border-color: var(--text);
}

/* -- scores -- */

.scores {
  width: 100%;
  display: flex;
  gap: 8px;
}

.score-box {
  flex: 1;
  background: var(--board-bg);
  border-radius: var(--radius);
  padding: 6px 10px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1px;
}

.score-label {
  font-size: 0.65rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: rgba(255, 255, 255, 0.65);
}

.score-value {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  font-weight: 700;
  color: #fff;
}

/* -- board -- */

.board-wrapper {
  position: relative;
  width: var(--board-size);
  height: var(--board-size);
}

.board {
  width: 100%;
  height: 100%;
  background: var(--board-bg);
  border-radius: var(--radius);
  padding: var(--cell-gap);
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(4, 1fr);
  gap: var(--cell-gap);
}

.cell {
  background: var(--cell-bg);
  border-radius: var(--radius);
}

/* -- tiles -- */

.tile {
  position: absolute;
  width: var(--cell-size);
  height: var(--cell-size);
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-weight: 700;
  color: var(--tile-text-dark);
  user-select: none;
  z-index: 10;
  transition: top 150ms ease-in-out, left 150ms ease-in-out;
}

.tile[data-value="2"]     { background: var(--tile-2);     font-size: 1.8rem; }
.tile[data-value="4"]     { background: var(--tile-4);     font-size: 1.8rem; }
.tile[data-value="8"]     { background: var(--tile-8);     font-size: 1.8rem; color: var(--tile-text-light); }
.tile[data-value="16"]    { background: var(--tile-16);    font-size: 1.6rem; color: var(--tile-text-light); }
.tile[data-value="32"]    { background: var(--tile-32);    font-size: 1.6rem; color: var(--tile-text-light); }
.tile[data-value="64"]    { background: var(--tile-64);    font-size: 1.6rem; color: var(--tile-text-light); }
.tile[data-value="128"]   { background: var(--tile-128);   font-size: 1.4rem; color: var(--tile-text-light); }
.tile[data-value="256"]   { background: var(--tile-256);   font-size: 1.4rem; color: var(--tile-text-light); }
.tile[data-value="512"]   { background: var(--tile-512);   font-size: 1.4rem; color: var(--tile-text-light); }
.tile[data-value="1024"]  { background: var(--tile-1024);  font-size: 1.15rem; color: var(--tile-text-light); }
.tile[data-value="2048"]  { background: var(--tile-2048);  font-size: 1.15rem; color: var(--tile-text-light); }
.tile[data-value="4096"]  { background: var(--tile-4096);  font-size: 1.05rem; color: var(--tile-text-light); }
.tile[data-value="8192"]  { background: var(--tile-8192);  font-size: 1.05rem; color: #fcedd0; box-shadow: 0 0 10px rgba(74, 40, 64, 0.45); }
.tile[data-value="16384"] { background: var(--tile-16384); font-size: 0.9rem;  color: #edd29e; border: 1px solid rgba(237, 210, 158, 0.45); box-shadow: 0 0 14px rgba(35, 42, 56, 0.55); }

/* understated 32,768 crimson-gold styling with calm ambient breathing and subtle shimmer */
.tile[data-value="32768"] {
  background: var(--tile-32768);
  font-size: 0.9rem;
  color: #fcedd0;
  border: 1px solid rgba(237, 194, 46, 0.65);
  animation: breathe-32k 3.5s ease-in-out infinite;
  position: absolute;
  overflow: hidden;
}

.tile[data-value="32768"]::after {
  content: '';
  position: absolute;
  inset: -60%;
  background: radial-gradient(circle, rgba(252, 237, 208, 0.16) 12%, transparent 60%);
  animation: slow-particle-drift 7s linear infinite;
  pointer-events: none;
}

@keyframes breathe-32k {
  0%, 100% {
    box-shadow: 0 0 12px rgba(180, 20, 50, 0.35), 0 0 20px rgba(237, 194, 46, 0.2);
  }
  50% {
    box-shadow: 0 0 20px rgba(180, 20, 50, 0.55), 0 0 32px rgba(237, 194, 46, 0.35);
  }
}

@keyframes slow-particle-drift {
  0%   { transform: rotate(0deg) translate(4px); }
  50%  { transform: rotate(180deg) translate(-4px); }
  100% { transform: rotate(360deg) translate(4px); }
}

/* understated 65,536 celestial obsidian styling with calm ethereal pulse and platinum aura */
.tile[data-value="65536"],
.tile-65536 {
  background: var(--tile-65536);
  font-size: 0.82rem;
  letter-spacing: -0.5px;
  color: #f0f6fc;
  border: 1px solid rgba(186, 230, 253, 0.65);
  animation: breathe-65k 4s ease-in-out infinite;
  position: absolute;
  overflow: hidden;
}

.tile[data-value="65536"]::after,
.tile-65536::after {
  content: '';
  position: absolute;
  inset: -60%;
  background: radial-gradient(circle, rgba(186, 230, 253, 0.18) 10%, transparent 65%);
  animation: slow-particle-drift 8s linear infinite;
  pointer-events: none;
}

@keyframes breathe-65k {
  0%, 100% {
    box-shadow: 0 0 12px rgba(14, 165, 233, 0.35), 0 0 24px rgba(224, 242, 254, 0.2);
  }
  50% {
    box-shadow: 0 0 22px rgba(14, 165, 233, 0.6), 0 0 36px rgba(224, 242, 254, 0.35);
  }
}

.tile-super {
  background: var(--tile-super) !important;
  color: var(--tile-text-light) !important;
  font-size: 0.85rem !important;
}

/* -- tile animations -- */

@keyframes tile-spawn {
  0%   { transform: scale(0); opacity: 0; }
  100% { transform: scale(1); opacity: 1; }
}

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

.tile-new {
  animation: tile-spawn 200ms ease;
}

.tile-merged {
  animation: tile-merge 100ms ease;
  z-index: 20;
}

/* -- game message overlay -- */

.game-message {
  display: none;
  position: absolute;
  inset: 0;
  border-radius: var(--radius);
  background: rgba(250, 248, 240, 0.75);
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
  z-index: 100;
}

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

.game-message p {
  font-family: var(--font-mono);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
}

.game-message .btn {
  flex: none;
  width: auto;
  padding: 10px 32px;
}

/* -- live decision telemetry -- */

.decision-hud {
  display: flex;
  width: 100%;
  flex-direction: column;
  gap: 6px;
}

.hud-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 2px;
}

.hud-mode-wrap {
  display: flex;
  align-items: center;
  gap: 6px;
}


.hud-mode {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.65rem;
  letter-spacing: 0.5px;
  color: var(--text);
  text-transform: lowercase;
}

.decision-hud.hud-mode-tablebase .hud-mode {
  color: #047857;
}

.decision-hud.hud-mode-wasm .hud-mode {
  color: #0369a1;
}

.hud-detail {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  color: var(--text-light);
  letter-spacing: 0.2px;
  text-transform: lowercase;
}

.hud-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
}

.hud-dir {
  background: var(--board-bg);
  border-radius: var(--radius);
  padding: 5px 4px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1px;
  transition: all 0.15s ease;
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.hud-dir-best {
  background: #8f7a66;
  border-color: #695a4c;
  box-shadow: 0 2px 6px rgba(119, 110, 101, 0.25);
}

.hud-dir-best .hud-label,
.hud-dir-best .hud-val,
.hud-dir-best .hud-prob {
  color: #fff !important;
  font-weight: 700;
}

.hud-dir-tablebase {
  background: #1b4d3e !important;
  border-color: #34d399 !important;
  box-shadow: 0 0 10px rgba(52, 211, 153, 0.35);
}

.hud-dir-tablebase .hud-label {
  color: #a7f3d0 !important;
}

.hud-dir-tablebase .hud-val {
  color: #d1fae5 !important;
}

.hud-dir-tablebase .hud-prob {
  color: #6ee7b7 !important;
}

.hud-dir-invalid {
  opacity: 0.35;
}

.hud-dir-danger {
  opacity: 0.75;
  border-color: rgba(180, 20, 50, 0.45);
}

.hud-dir-danger .hud-val,
.hud-dir-danger .hud-prob {
  color: #ff8a8a !important;
}

.hud-label {
  font-size: 0.62rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 1.2px;
  color: rgba(255, 255, 255, 0.65);
}

.hud-val {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  font-weight: 700;
  color: #fff;
  white-space: nowrap;
}

.hud-prob {
  font-family: var(--font-mono);
  font-size: 0.62rem;
  color: rgba(255, 255, 255, 0.75);
  white-space: nowrap;
  letter-spacing: 0.4px;
}

/* -- buttons -- */

.controls {
  width: 100%;
  display: flex;
  gap: 8px;
}

.btn {
  flex: 1;
  padding: 8px 12px;
  border: 2px solid var(--board-bg);
  border-radius: var(--radius);
  background: none;
  color: var(--text);
  font-family: var(--font-body);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.btn:hover {
  background: var(--board-bg);
  color: #fff;
}

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

.btn-primary:hover {
  background: var(--text);
  border-color: var(--text);
}

.btn-turbo {
  background: var(--tile-8) !important;
  border-color: var(--tile-8) !important;
  color: var(--tile-text-light) !important;
}

.btn-turbo:hover {
  background: var(--tile-16) !important;
  border-color: var(--tile-16) !important;
}

.board.turbo .tile {
  transition: top 50ms linear, left 50ms linear;
}

.btn:focus-visible,
.btn-nerds:focus-visible,
.btn-icon:focus-visible {
  outline: 2px solid var(--text);
  outline-offset: 2px;
}



/* -- footer -- */

.footer {
  position: fixed;
  bottom: 10px;
  left: 0;
  width: 100%;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--text-light);
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 6px;
  letter-spacing: 0.2px;
  z-index: 10;
  pointer-events: none;
}

.footer span,
.footer a {
  pointer-events: auto;
}

.footer a {
  color: var(--text);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.15s ease;
}

.footer a:hover {
  color: var(--tile-64);
  text-decoration: underline;
}

.footer-sep {
  color: var(--text-light);
  opacity: 0.6;
}

.version-tag {
  color: var(--text-light);
  font-weight: 500;
}


/* -- modal -- */

.modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.4);
  z-index: 1000;
  justify-content: center;
  align-items: center;
  padding: 20px;
  backdrop-filter: blur(2px);
}

.modal-overlay.active {
  display: flex;
}

.modal {
  position: relative;
  background: var(--bg);
  border-radius: 10px;
  padding: 28px 24px;
  max-width: 480px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
}

.modal-close {
  position: absolute;
  top: 14px;
  right: 14px;
}

.modal-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 18px;
  border-bottom: 1px solid rgba(187, 173, 160, 0.3);
  padding-bottom: 10px;
}

.modal-tab {
  background: none;
  border: none;
  font-family: var(--font-body);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-light);
  cursor: pointer;
  padding: 6px 12px;
  border-radius: 12px;
  transition: all 0.15s ease;
}

.modal-tab.active {
  color: var(--text);
  background: rgba(187, 173, 160, 0.22);
}

.modal-tab:hover:not(.active) {
  color: var(--text);
}

.modal-tab-content {
  display: none;
  font-size: 0.88rem;
  line-height: 1.6;
  color: var(--text);
}

.modal-tab-content.active {
  display: block;
}

.modal-tab-content h2 {
  font-family: var(--font-mono);
  font-size: 1.15rem;
  margin-bottom: 12px;
  color: var(--text);
}

.modal-tab-content h3 {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  margin-top: 16px;
  margin-bottom: 6px;
  color: var(--text);
}

.modal-tab-content p {
  margin-bottom: 12px;
}

.modal-list {
  margin: 10px 0 16px 20px;
  font-size: 0.84rem;
  line-height: 1.6;
}

.modal-list li {
  margin-bottom: 6px;
}

.score-card-images {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin: 16px 0;
}

.score-card-images figure {
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.score-card-images img {
  width: 100%;
  height: auto;
  border-radius: 6px;
  border: 1px solid rgba(187, 173, 160, 0.4);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
}

.score-card-images figcaption {
  font-size: 0.72rem;
  color: var(--text-light);
  text-align: center;
  line-height: 1.3;
}

.modal-tab-content a {
  color: var(--text);
  font-weight: 600;
}

/* -- responsive -- */

@media (max-width: 640px) {
  :root {
    --board-size: min(310px, calc(100vw - 24px), calc(100vh - 230px));
    --cell-gap: 6px;
  }

  body {
    padding: 8px 10px;
  }

  .title {
    font-size: 1.6rem;
  }

  .score-value {
    font-size: 1.05rem;
  }

  .footer {
    font-size: 0.62rem;
    gap: 4px;
  }

  .controls .btn {
    padding: 7px 4px;
    font-size: 0.74rem;
  }

  .hud-dir {
    padding: 4px 2px;
  }

  .hud-label {
    font-size: 0.52rem;
  }

  .hud-val {
    font-size: 0.65rem;
  }

  .hud-prob {
    font-size: 0.52rem;
  }

  .tile[data-value="32768"],
  .tile[data-value="65536"],
  .tile-65536 {
    font-size: 0.72rem;
    letter-spacing: -0.6px;
  }

  .score-card-images {
    grid-template-columns: 1fr;
  }

  .latency-badge {
    font-size: 0.65rem;
    padding: 3px 6px;
  }

  .btn-nerds {
    font-size: 0.65rem;
    padding: 3px 7px;
  }
}