:root{
    --font-display: 'Fraunces', serif;
    --font-ui:      'Space Grotesk', sans-serif;
    --font-num:     'JetBrains Mono', monospace;
  }

  :root[data-theme="dark"]{
    --bg-grad-a:    #103a40;
    --bg-grad-b:    #071e21;
    --glass:        rgba(18, 59, 65, 0.55);
    --glass-strong: rgba(27, 75, 82, 0.65);
    --glass-border: rgba(242, 166, 90, 0.18);
    --glass-border-soft: rgba(111, 168, 173, 0.14);
    --cell-bg:      rgba(255,255,255,0.04);
    --amber:        #F2A65A;
    --amber-hot:    #FFD166;
    --cream:        #F7F3E8;
    --muted:        #9FC6C9;
    --danger:       #E9724C;
    --overlay-bg:   rgba(7, 30, 33, 0.72);
  }

  :root[data-theme="light"]{
    --bg-grad-a:    #FCEFE0;
    --bg-grad-b:    #F4DCC0;
    --glass:        rgba(255, 255, 255, 0.55);
    --glass-strong: rgba(255, 255, 255, 0.72);
    --glass-border: rgba(180, 110, 40, 0.18);
    --glass-border-soft: rgba(120, 90, 50, 0.12);
    --cell-bg:      rgba(90, 50, 10, 0.05);
    --amber:        #C97A2B;
    --amber-hot:    #A85E1B;
    --cream:        #2C231B;
    --muted:        #7A6650;
    --danger:       #C1442A;
    --overlay-bg:   rgba(252, 239, 224, 0.82);
  }

  *{ box-sizing: border-box; -webkit-tap-highlight-color: transparent; }

  html, body{
    margin:0;
    min-height:100%;
    background: radial-gradient(ellipse at top, var(--bg-grad-a) 0%, var(--bg-grad-b) 100%);
    color: var(--cream);
    font-family: var(--font-ui);
    overflow-x:hidden;
    transition: background 0.3s ease, color 0.3s ease;
  }

  body{
    display:flex;
    flex-direction:column;
    min-height:100dvh;
  }

  a{ color:inherit; }

    /* ---------- site header / footer ---------- */

  .site-header{
    display:flex;
    justify-content:center;
    padding: 14px max(16px, env(safe-area-inset-left)) 14px max(16px, env(safe-area-inset-right));
    background: var(--glass);
    backdrop-filter: blur(18px) saturate(160%);
    -webkit-backdrop-filter: blur(18px) saturate(160%);
    border-bottom: 1px solid var(--glass-border);
  }

  .header-inner{
    display:flex;
    align-items:center;
    justify-content:space-between;
    gap: 8px;
    width: 100%;
  }

  .site-header .logo{
    display:flex;
    align-items:center;
    gap: 8px;
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 1.6rem;
    text-decoration:none;
  }

  .site-header .logo-badge{
    width: 40px;
    height: 40px;
    border-radius: 10px;
    background: linear-gradient(160deg, var(--amber-hot), var(--amber));
    display:flex;
    align-items:center;
    justify-content:center;
    font-family: var(--font-num);
    font-weight: 800;
    font-size: 1.1rem;
    color: #10262a;
    flex-shrink: 0;
  }

  .site-header .logo .accent{ color: var(--amber-hot); }

  .site-header .domain{
    font-family: var(--font-num);
    font-size: 0.68rem;
    letter-spacing: 1px;
    color: var(--muted);
    display: none;
  }

  @media (min-width: 480px){
    .site-header .domain{ display:inline; }
  }

  .icon-btn{
    background: var(--glass-strong);
    border: 1px solid var(--glass-border);
    color: var(--cream);
    width: 40px;
    height: 40px;
    border-radius: 11px;
    display:flex;
    align-items:center;
    justify-content:center;
    font-size: 1.05rem;
    cursor:pointer;
    transition: transform 0.12s ease, background 0.12s ease;
  }

  .icon-btn:hover{ transform: translateY(-1px); }
  .icon-btn:active{ transform: translateY(0); }
  .icon-btn:focus-visible{ outline: 2px solid var(--amber-hot); outline-offset:2px; }

  .header-actions{ display:flex; gap:14px; align-items:center; }

  @media (min-width: 951px){
    .header-inner{ max-width: 950px; }
  }

  main{
    flex: 1;
    display:flex;
    align-items:center;
    justify-content:center;
    padding: 24px 16px;
  }

  .site-footer{
    padding: 18px max(20px, env(safe-area-inset-left)) max(22px, env(safe-area-inset-bottom));
    text-align:center;
    font-size: 0.72rem;
    color: var(--muted);
    background: var(--glass);
    backdrop-filter: blur(18px) saturate(160%);
    -webkit-backdrop-filter: blur(18px) saturate(160%);
    border-top: 1px solid var(--glass-border-soft);
  }

  .site-footer .footer-domain{ color: var(--amber); font-family: var(--font-num); }

  .site-footer .footer-links{
    margin-top: 8px;
    display:flex;
    gap: 16px;
    justify-content:center;
    flex-wrap: wrap;
  }

  .site-footer .footer-links a{ color: var(--muted); text-decoration:none; }
  .site-footer .footer-links a:hover{ color: var(--amber-hot); }
  /* ---------- game card (glass) ---------- */

  .cabinet{
    width: min(94vw, 460px);
    padding: 24px 20px 28px;
    background: var(--glass);
    backdrop-filter: blur(22px) saturate(170%);
    -webkit-backdrop-filter: blur(22px) saturate(170%);
    border-radius: 24px;
    border: 1px solid var(--glass-border);
    box-shadow:
      0 30px 60px -25px rgba(0,0,0,0.45),
      inset 0 1px 0 rgba(255,255,255,0.08);
    position: relative;
  }

  .cabinet-header{
    display:flex;
    justify-content:space-between;
    align-items:flex-end;
    margin-bottom: 18px;
    gap: 10px;
  }

  h1{
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 2.3rem;
    letter-spacing: 0.5px;
    margin: 0;
    line-height: 1;
  }

  h1 span{ color: var(--amber-hot); }

  .subtitle{
    font-size: 0.68rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--muted);
    margin-top: 6px;
  }

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

  .score-box{
    background: var(--glass-strong);
    border-radius: 5px;
    padding: 7px 12px;
    text-align:center;
    min-width: 62px;
    border: 1px solid var(--glass-border-soft);
  }

  .score-box .label{
    font-size: 0.58rem;
    letter-spacing: 1.5px;
    text-transform: uppercase;
    color: var(--muted);
  }

  .score-box .value{
    font-family: var(--font-num);
    font-weight: 700;
    font-size: 1.05rem;
    color: var(--amber-hot);
  }

  .controls-row{
    display:flex;
    justify-content:space-between;
    align-items:center;
    margin-bottom: 14px;
    gap: 8px;
  }

  .hint{ font-size: 0.72rem; color: var(--muted); }

  .row-actions{ display:flex; gap:8px; }

  button.pill{
    font-family: var(--font-ui);
    font-weight: 600;
    font-size: 0.78rem;
    background: var(--amber);
    color: #10262a;
    border: none;
    padding: 8px 14px;
    border-radius: 5px;
    cursor: pointer;
    transition: transform 0.12s ease, background 0.12s ease;
  }

  :root[data-theme="light"] button.pill{ color: #FCEFE0; }

  button.pill:hover{ background: var(--amber-hot); transform: translateY(-1px); }
  button.pill:active{ transform: translateY(0); }
  button.pill:focus-visible{ outline: 2px solid var(--cream); outline-offset: 2px; }

  button.pill.ghost{
    background: rgb(9 78 28 / 93%);
    color: var(--cream);
    border: 1px solid var(--glass-border-soft);
  }

  .board-wrap{ position: relative; touch-action: none; }

  .board{
    display:grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(4, 1fr);
    gap: 10px;
    background: var(--cell-bg);
    padding: 10px;
    border-radius: 16px;
    aspect-ratio: 1 / 1;
    box-shadow: inset 0 2px 10px rgba(0,0,0,0.15);
  }

  .cell-bg{ background: rgb(76 8 8 / 8%); border-radius: 8px; }

  .tiles-layer{top:10px; left:10px; right:10px; bottom:10px; }

  .tile{
    position:absolute;
    display:flex;
    align-items:center;
    justify-content:center;
    border-radius: 8px;
    font-family: var(--font-num);
    font-weight: 700;
    transition: top 0.13s ease, left 0.13s ease, transform 0.13s ease, opacity 0.13s ease;
    user-select:none;
    box-shadow: 0 2px 6px rgba(0,0,0,0.15), inset 0 1px 0 rgba(255,255,255,0.15);
  }

  .tile.spawn{ animation: pop 0.16s ease; }
  .tile.merged{ animation: merge-pulse 0.18s ease; }
  .tile.leaving{ opacity: 0; transform: scale(0.9); }

  @keyframes pop{
    0%{ transform: scale(0.55); opacity: 0.4; }
    100%{ transform: scale(1); opacity: 1; }
  }

  @keyframes merge-pulse{
    0%{ transform: scale(1); }
    40%{ transform: scale(1.16); }
    100%{ transform: scale(1); }
  }

  .overlay{
    position:absolute;
    inset: 0;
    background: var(--overlay-bg);
    border-radius: 16px;
    display:none;
    flex-direction:column;
    align-items:center;
    justify-content:center;
    gap: 12px;
    text-align:center;
    backdrop-filter: blur(6px);
    padding: 20px;
  }

  .overlay.show{ display:flex; }

  .overlay .msg{ font-family: var(--font-display); font-size: 1.6rem; font-weight: 700; }
  .overlay .msg.win{ color: var(--amber-hot); }
  .overlay .msg.lose{ color: var(--danger); }

  .overlay .final-score{ font-family: var(--font-num); color: var(--muted); font-size: 0.85rem; }

  .name-row{ display:flex; gap: 8px; margin-top: 4px; }

  .name-row input{
    font-family: var(--font-ui);
    background: var(--glass-strong);
    border: 1px solid var(--glass-border-soft);
    color: var(--cream);
    border-radius: 10px;
    padding: 8px 10px;
    width: 130px;
    font-size: 0.82rem;
  }

  .name-row input:focus-visible{ outline: 2px solid var(--amber-hot); }

  .overlay-actions{ display:flex; gap: 8px; flex-wrap: wrap; justify-content:center; margin-top: 6px; }

  footer.instructions{
    margin-top: 14px;
    font-size: 0.7rem;
    color: var(--muted);
    text-align:center;
    line-height: 1.5;
  }

  /* ---------- leaderboard modal ---------- */

  .modal-backdrop{
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.45);
    display:none;
    align-items:center;
    justify-content:center;
    z-index: 50;
    padding: 20px;
  }

  .modal-backdrop.show{ display:flex; }

  .modal{
    width: min(92vw, 380px);
    max-height: 80vh;
    overflow-y: auto;
    background: var(--glass-strong);
    backdrop-filter: blur(24px) saturate(180%);
    -webkit-backdrop-filter: blur(24px) saturate(180%);
    border: 1px solid var(--glass-border);
    border-radius: 18px;
    padding: 20px;
  }

  .modal h2{
    font-family: var(--font-display);
    margin: 0 0 12px;
    font-size: 1.3rem;
  }

  .modal ol{ list-style:none; margin:0; padding:0; }

  .modal li{
    display:flex;
    justify-content:space-between;
    padding: 8px 4px;
    border-bottom: 1px solid var(--glass-border-soft);
    font-size: 0.88rem;
  }

  .modal li:last-child{ border-bottom:none; }
  .modal li .rank{ color: var(--muted); width: 24px; }
  .modal li .name{ flex:1; }
  .modal li .pts{ font-family: var(--font-num); color: var(--amber-hot); font-weight:700; }

  .modal .empty{ color: var(--muted); font-size: 0.85rem; text-align:center; padding: 12px 0; }

  .modal-close{
    margin-top: 14px;
    width: 100%;
  }

  /* ---------- toast ---------- */

  .toast{
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%) translateY(10px);
    background: var(--glass-strong);
    border: 1px solid var(--glass-border);
    color: var(--cream);
    padding: 10px 18px;
    border-radius: 12px;
    font-size: 0.82rem;
    opacity: 0;
    pointer-events:none;
    transition: opacity 0.2s ease, transform 0.2s ease;
    z-index: 60;
    backdrop-filter: blur(16px);
  }

  .toast.show{ opacity: 1; transform: translateX(-50%) translateY(0); }

  /* fullscreen mobile experience */
  :fullscreen main{ padding: 12px; }
  :fullscreen .site-header, :fullscreen .site-footer{ display:none; }

  @media (max-width: 420px){
    .cabinet{ width: 100%; border-radius: 18px; padding: 18px 14px 22px; }
    h1{ font-size: 1.9rem; }
  }

  @media (prefers-reduced-motion: reduce){
    .tile, .tile-inner{ animation: none !important; transition: none !important; }
  }
  
  /* ---------- info / SEO content section ---------- */

  .info-section{
    padding: 8px 16px 40px;
    display:flex;
    justify-content:center;
  }

  .info-inner{
    width: 100%;
    max-width: 700px;
  }

  .info-inner h2{
    font-family: var(--font-display);
    font-size: 1.35rem;
    margin: 34px 0 10px;
  }

  .info-inner h2:first-child{ margin-top: 0; }

  .info-inner p{
    font-size: 0.92rem;
    line-height: 1.65;
    color: var(--cream);
    margin: 0 0 8px;
  }

  .tips-list{
    margin: 0;
    padding-left: 20px;
    font-size: 0.92rem;
    line-height: 1.7;
  }

  .tips-list li{ margin-bottom: 4px; }

  .faq details{
    background: var(--glass);
    border: 1px solid var(--glass-border-soft);
    border-radius: 12px;
    padding: 12px 16px;
    margin-bottom: 10px;
  }

  .faq summary{
    cursor:pointer;
    font-weight: 600;
    font-size: 0.94rem;
    list-style: none;
  }

  .faq summary::-webkit-details-marker{ display:none; }

  .faq summary::before{
    content: "+";
    color: var(--amber-hot);
    display:inline-block;
    width: 16px;
    font-weight: 700;
  }

  .faq details[open] summary::before{ content: "–"; }

  .faq details p{
    margin: 10px 0 0;
    font-size: 0.88rem;
    color: var(--muted);
  }

  @media (min-width: 951px){
    .info-inner{ max-width: 950px; }
  }