* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;

  display: grid;
  place-items: center;

  background: #111827;

  font-family: Arial, sans-serif;

  transition: background 0.25s ease;
}

.game {
  width: min(92vw, 400px);
  text-align: center;
}

h1 {
  margin: 0 0 18px;

  color: #ffffff;

  font-size: 28px;
}

/* --------------------------------
   Difficulty
-------------------------------- */

.difficulty {
  display: grid;
  grid-template-columns: repeat(4, 1fr);

  gap: 6px;
  margin-bottom: 8px;
}

.difficulty-button {
  border: 0;
  border-radius: 8px;

  padding: 9px 5px;

  background: #374151;
  color: #9ca3af;

  font-size: 14px;
  font-weight: bold;

  cursor: pointer;

  transition:
    background 0.15s ease,
    color 0.15s ease,
    transform 0.1s ease;
}

.difficulty-button.active {
  background: var(--accent);
  color: white;
}

.difficulty-button:active {
  transform: scale(0.96);
}


/* --------------------------------
   Themes
-------------------------------- */

.themes {
  display: none;

  grid-template-columns: repeat(4, 1fr);

  gap: 5px;
  margin-bottom: 8px;
}

.themes.visible {
  display: grid;
}

.theme-button {
  border: 0;
  border-radius: 7px;

  padding: 7px 3px;

  background: var(--panel);
  color: var(--text-muted);

  font-size: 12px;
  font-weight: bold;

  cursor: pointer;
}

.theme-button.active {
  background: var(--accent);
  color: white;
}

.theme-button.locked {
  opacity: 0.55;
  cursor: default;
}


/* --------------------------------
   Controls
-------------------------------- */

.controls {
  display: flex;
  align-items: center;
  justify-content: space-between;

  margin-bottom: 12px;
  gap: 10px;
}

.shuffle {
  border: 0;
  border-radius: 9px;

  padding: 10px 16px;

  background: var(--accent);
  color: white;

  font-size: 16px;
  font-weight: bold;

  cursor: pointer;

  transition: transform 0.1s ease;
}

.shuffle:active {
  transform: scale(0.95);
}


/* --------------------------------
   Scores
-------------------------------- */

.stats {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.best,
.moves {
  color: var(--text);
  font-size: 15px;
  font-weight: bold;
}


/* --------------------------------
   Board
-------------------------------- */



.mystery-goal {
  display: none;

  margin-bottom: 10px;
  padding: 7px;

  text-align: center;

  background: var(--panel);
  color: var(--text-muted);

  border-radius: 8px;

  font-size: 13px;
  font-weight: bold;
}

.mystery-goal.visible {
  display: block;
}


/* --------------------------------
   Mystery board rotation
-------------------------------- */

.board.mystery-rotating {
  transform: rotate(90deg);
}

.board {
  width: 100%;
  aspect-ratio: 1;

  padding: 6px;

  display: grid;
  gap: 6px;

  background: var(--board);
  border-radius: 14px;

  transition:
    background 0.25s ease,
    transform 0.45s ease;
}


/* --------------------------------
   Tiles
-------------------------------- */

.tile {
  display: grid;
  place-items: center;

  background: var(--tile);
  color: var(--tile-text);

  font-size: clamp(20px, 8vw, 36px);
  font-weight: bold;

  border-radius: 9px;

  cursor: pointer;
  user-select: none;

  transition:
    transform 0.14s ease,
    background 0.25s ease;
}

.tile:active {
  transform: scale(0.93);
}


/* Empty cell */

.empty {
  background: var(--empty);
  cursor: default;
}


/* --------------------------------
   Illegal move
-------------------------------- */

.tile.shake {
  animation: shake 0.22s ease;
}

@keyframes shake {

  0% {
    transform: translateX(0);
  }

  25% {
    transform: translateX(-5px);
  }

  50% {
    transform: translateX(5px);
  }

  75% {
    transform: translateX(-4px);
  }

  100% {
    transform: translateX(0);
  }
}


/* --------------------------------
   Win animation
-------------------------------- */

.tile.win {
  animation: winTile 0.45s ease;
  background: var(--win);
}

@keyframes winTile {

  0% {
    transform: scale(1);
  }

  50% {
    transform: scale(1.12);
  }

  100% {
    transform: scale(1);
  }
}


/* --------------------------------
   Unlock message
-------------------------------- */

.unlock-message {
  display: none;

  margin-top: 10px;

  padding: 10px;

  text-align: center;

  color: var(--win);

  background: var(--panel);

  border-radius: 9px;

  font-size: 15px;
  font-weight: bold;
}


/* --------------------------------
   Win screen
-------------------------------- */

.win-message {
  display: none;

  margin-top: 14px;
  padding: 18px;

  text-align: center;

  background: var(--panel);

  border: 1px solid var(--board);

  border-radius: 14px;
}

.win-title {
  color: var(--win);

  font-size: 25px;
  font-weight: bold;

  margin-bottom: 14px;
}

.win-stats {
  display: flex;
  justify-content: center;

  gap: 35px;

  color: var(--text-muted);

  font-size: 14px;
}

.win-stats strong {
  display: block;

  margin-top: 4px;

  color: var(--text);

  font-size: 22px;
}

.new-puzzle {
  margin-top: 16px;

  border: 0;
  border-radius: 9px;

  padding: 10px 18px;

  background: var(--accent);
  color: white;

  font-size: 15px;
  font-weight: bold;

  cursor: pointer;
}

.new-puzzle:active {
  transform: scale(0.95);
}

/*

home-btn 
*/
.home-btn {
  position: fixed;
  top: max(12px, env(safe-area-inset-top));
  left: 12px;

  z-index: 1000;

  display: inline-flex;
  align-items: center;
  gap: 6px;

  padding: 8px 11px;

  border: 1px solid rgba(255,255,255,.1);
  border-radius: 12px;

  background: rgba(15,18,32,.82);
  color: rgba(255,255,255,.8);

  text-decoration: none;

  font-family:
    -apple-system,
    BlinkMacSystemFont,
    "Segoe UI",
    Roboto,
    Helvetica,
    Arial,
    sans-serif;

  font-size: 10px;
  font-weight: 700;
  letter-spacing: .08em;

  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);

  box-shadow: 0 4px 18px rgba(0,0,0,.2);

  transition:
    transform .15s ease,
    background .15s ease,
    color .15s ease;
}

.home-btn svg {
  width: 15px;
  height: 15px;

  fill: none;
  stroke: currentColor;

  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.home-btn:active {
  transform: scale(.93);
}

.home-btn:hover {
  background: rgba(255,255,255,.1);
  color: white;
}


/* =================================
   THEMES
================================= */


/* Classic */

body[data-theme="classic"] {
  --accent: #60a5fa;
  --board: #374151;
  --tile: #60a5fa;
  --tile-text: #ffffff;
  --empty: #555555;
  --panel: #1f2937;
  --text: #ffffff;
  --text-muted: #9ca3af;
  --win: #4ade80;
}


/* Neon */

body[data-theme="neon"] {
  --accent: #c026d3;
  --board: #291338;
  --tile: #a855f7;
  --tile-text: #ffffff;
  --empty: #17101d;
  --panel: #24112f;
  --text: #ffffff;
  --text-muted: #d8b4fe;
  --win: #22d3ee;
}


/* Forest */

body[data-theme="forest"] {
  --accent: #22c55e;
  --board: #24372b;
  --tile: #16a34a;
  --tile-text: #ffffff;
  --empty: #17231b;
  --panel: #1d3024;
  --text: #ffffff;
  --text-muted: #a7c9ae;
  --win: #bef264;
}


/* Sunset */

body[data-theme="sunset"] {
  --accent: #f97316;
  --board: #43251f;
  --tile: #f97316;
  --tile-text: #ffffff;
  --empty: #241512;
  --panel: #351d19;
  --text: #ffffff;
  --text-muted: #fdba74;
  --win: #facc15;
}


/* --------------------------------
   Small screens
-------------------------------- */

@media (max-width: 350px) {

  .difficulty {
    grid-template-columns: repeat(2, 1fr);
  }

  .controls {
    align-items: flex-start;
  }

  .stats {
    justify-content: flex-end;
  }

  .best,
  .moves {
    font-size: 13px;
  }

  .difficulty-button {
    font-size: 13px;
  }

  .theme-button {
    font-size: 11px;
  }
}