:root{
  --bg:#0b1020; --bg2:#121933; --card:#161f3d; --card2:#1d2850;
  --ink:#eef2ff; --muted:#9aa6c7; --line:#26315c;
  --accent:#6d8bff; --accent2:#4ade80; --warn:#fbbf24; --danger:#f87171;
  --wU:#f8fafc; --wD:#ffd500; --wR:#c8102e; --wL:#ff5800; --wF:#009e60; --wB:#0051ba;
  --radius:16px; --safe-b:env(safe-area-inset-bottom,0px);
  --tab-h:64px;
}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;padding:0;background:var(--bg);color:var(--ink);
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Inter,system-ui,sans-serif;
  overscroll-behavior-y:none}
body{max-width:720px;margin:0 auto;min-height:100vh}
a{color:var(--accent);text-decoration:none}
h1,h2,h3{line-height:1.2;margin:0 0 .4em}
h1{font-size:1.5rem} h2{font-size:1.2rem} h3{font-size:1rem}
p{line-height:1.55;color:var(--ink)}
small{color:var(--muted)}

/* App header */
.appbar{position:sticky;top:0;z-index:20;background:rgba(11,16,32,.85);
  backdrop-filter:blur(10px);border-bottom:1px solid var(--line);
  padding:12px 16px calc(12px);display:flex;align-items:center;gap:10px;
  padding-top:calc(12px + env(safe-area-inset-top,0px))}
.appbar .logo{width:28px;height:28px;border-radius:7px;flex:0 0 auto;
  background:conic-gradient(from 45deg,var(--wF),var(--wU),var(--wR),var(--wD),var(--wF))}
.appbar .title{font-weight:700;font-size:1.05rem}
.appbar .spacer{flex:1}
.pill{font-size:.72rem;color:var(--muted);border:1px solid var(--line);
  padding:4px 9px;border-radius:999px;display:inline-flex;gap:6px;align-items:center}

/* Views */
main{padding:16px 16px calc(var(--tab-h) + 24px + var(--safe-b))}
.view{display:none;animation:fade .25s ease}
.view.active{display:block}
@keyframes fade{from{opacity:0;transform:translateY(6px)}to{opacity:1}}

/* Cards */
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:16px;margin:0 0 14px}
.card.tap{cursor:pointer;transition:transform .08s ease,border-color .15s}
.card.tap:active{transform:scale(.99)}
.card.tap:hover{border-color:var(--accent)}
.row{display:flex;align-items:center;gap:12px}
.grow{flex:1;min-width:0}
.muted{color:var(--muted)}
.center{text-align:center}
.chips{display:flex;flex-wrap:wrap;gap:8px;margin:8px 0}
.chip{font-size:.75rem;background:var(--card2);border:1px solid var(--line);
  color:var(--muted);padding:5px 10px;border-radius:999px}
.chip.done{color:var(--accent2);border-color:#2e5b45}

/* Levels / lessons list */
.level-head{display:flex;align-items:center;gap:10px;margin:22px 4px 10px}
.level-head .badge{width:30px;height:30px;border-radius:9px;display:grid;place-items:center;
  font-weight:800;background:var(--card2);border:1px solid var(--line);color:var(--accent)}
.level-head .sub{font-size:.8rem}
.lesson{display:flex;align-items:center;gap:12px}
.lesson .num{width:34px;height:34px;border-radius:10px;flex:0 0 auto;display:grid;place-items:center;
  font-weight:700;background:var(--card2);border:1px solid var(--line)}
.lesson.done .num{background:#173a2a;border-color:#2e5b45;color:var(--accent2)}
.lesson .arrow{color:var(--muted)}
.progress{height:8px;background:var(--card2);border-radius:999px;overflow:hidden;border:1px solid var(--line)}
.progress > i{display:block;height:100%;background:linear-gradient(90deg,var(--accent),var(--accent2));width:0}

/* Buttons */
.btn{appearance:none;border:1px solid var(--line);background:var(--card2);color:var(--ink);
  font:inherit;font-weight:600;padding:12px 16px;border-radius:12px;cursor:pointer;
  display:inline-flex;align-items:center;justify-content:center;gap:8px;transition:transform .08s,background .15s}
.btn:active{transform:scale(.98)}
.btn.primary{background:linear-gradient(90deg,var(--accent),#8aa0ff);border-color:transparent;color:#0b1020}
.btn.good{background:linear-gradient(90deg,#34d399,#4ade80);border-color:transparent;color:#062017}
.btn.ghost{background:transparent}
.btn.block{width:100%}
.btn.sm{padding:8px 12px;font-size:.85rem;border-radius:10px}
.btn:disabled{opacity:.4;pointer-events:none}
.btnrow{display:flex;gap:10px;flex-wrap:wrap}

/* Notation / algorithm cards */
.alg{background:#0e1530;border:1px solid var(--line);border-radius:12px;padding:12px 14px;margin:12px 0}
.alg .label{font-size:.72rem;text-transform:uppercase;letter-spacing:.08em;color:var(--muted)}
.alg .moves{font-family:"SF Mono",ui-monospace,Menlo,Consolas,monospace;font-size:1.15rem;
  font-weight:700;letter-spacing:.06em;margin:6px 0 10px;word-spacing:.15em}
.alg .moves .m{padding:1px 3px;border-radius:5px}
.alg .moves .m.hot{background:var(--accent);color:#0b1020}
.note{border-left:3px solid var(--warn);background:rgba(251,191,36,.08);
  padding:10px 12px;border-radius:0 10px 10px 0;margin:12px 0;font-size:.92rem}
.tip{border-left-color:var(--accent2);background:rgba(74,222,128,.08)}
ul.clean{margin:.4em 0;padding-left:1.15em}
ul.clean li{margin:.35em 0;line-height:1.5}

/* Face diagram (2D) */
.facewrap{display:flex;gap:16px;flex-wrap:wrap;align-items:center;justify-content:center;margin:14px 0}
.face{display:grid;grid-template-columns:repeat(3,26px);grid-template-rows:repeat(3,26px);
  gap:4px;padding:6px;background:#0e1530;border:1px solid var(--line);border-radius:12px}
.face i{border-radius:5px;border:1px solid rgba(0,0,0,.35)}
.facecap{font-size:.72rem;color:var(--muted);text-align:center;margin-top:4px}

/* Cube tab */
#cubeCanvasWrap{position:relative;width:100%;height:min(56vw,360px);
  background:radial-gradient(circle at 50% 40%,#182146,#0b1020 70%);
  border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;touch-action:none}
#cubeCanvasWrap canvas{display:block;width:100%;height:100%}
.movepad{display:grid;grid-template-columns:repeat(6,1fr);gap:8px;margin-top:12px}
.movepad .btn{padding:12px 0;font-weight:800;font-family:ui-monospace,monospace}
.seqbar{display:flex;gap:8px;align-items:center;margin-top:10px;flex-wrap:wrap}

/* Timer */
.timer-display{font-variant-numeric:tabular-nums;font-weight:800;text-align:center;
  font-size:19vw;line-height:1;letter-spacing:-.02em;margin:10px 0}
@media(min-width:520px){.timer-display{font-size:96px}}
.timer-display.ready{color:var(--danger)}
.timer-display.set{color:var(--accent2)}
.scramble{font-family:ui-monospace,monospace;font-size:1.05rem;text-align:center;
  line-height:1.7;color:var(--ink);word-spacing:.2em}
.stat{flex:1;text-align:center}
.stat b{display:block;font-size:1.25rem}
.times-list{display:flex;flex-wrap:wrap;gap:8px;margin-top:10px}
.time-tag{font-family:ui-monospace,monospace;background:var(--card2);border:1px solid var(--line);
  border-radius:9px;padding:6px 10px;font-size:.85rem}

/* Bottom tab bar */
.tabbar{position:fixed;bottom:0;left:50%;transform:translateX(-50%);width:100%;max-width:720px;
  height:calc(var(--tab-h) + var(--safe-b));padding-bottom:var(--safe-b);
  background:rgba(11,16,32,.92);backdrop-filter:blur(12px);border-top:1px solid var(--line);
  display:flex;z-index:30}
.tabbar button{flex:1;background:none;border:0;color:var(--muted);font:inherit;font-size:.68rem;
  display:flex;flex-direction:column;align-items:center;justify-content:center;gap:3px;cursor:pointer;padding:6px 0}
.tabbar button svg{width:22px;height:22px;stroke:currentColor;fill:none;stroke-width:1.9}
.tabbar button.active{color:var(--accent)}

/* Install prompt */
.install{position:fixed;left:12px;right:12px;bottom:calc(var(--tab-h) + 12px + var(--safe-b));
  max-width:696px;margin:0 auto;background:var(--card2);border:1px solid var(--accent);
  border-radius:14px;padding:12px 14px;display:none;align-items:center;gap:12px;z-index:40;
  box-shadow:0 12px 40px rgba(0,0,0,.5)}
.install.show{display:flex}
.sheet-back{position:fixed;inset:0;background:rgba(4,7,18,.6);z-index:50;display:none}
.sheet-back.show{display:block}
.sheet{position:fixed;left:0;right:0;bottom:0;max-width:720px;margin:0 auto;background:var(--bg2);
  border-top-left-radius:22px;border-top-right-radius:22px;border:1px solid var(--line);
  z-index:60;transform:translateY(100%);transition:transform .28s ease;max-height:92vh;overflow:auto;
  padding:8px 16px calc(24px + var(--safe-b))}
.sheet.show{transform:translateY(0)}
.sheet .grab{width:44px;height:5px;border-radius:999px;background:var(--line);margin:10px auto 6px}
.lesson-top{display:flex;align-items:center;gap:10px;position:sticky;top:0;background:var(--bg2);
  padding:8px 0;z-index:2;border-bottom:1px solid var(--line);margin-bottom:8px}
.x{margin-left:auto;background:var(--card);border:1px solid var(--line);color:var(--ink);
  width:34px;height:34px;border-radius:10px;font-size:1.1rem;cursor:pointer}
.hidden{display:none!important}

/* subheader with back button */
.subhead{display:flex;align-items:center;gap:10px;margin-bottom:6px}
.subhead h2{margin:0}

/* segmented control */
.seg{display:flex;gap:6px;background:var(--card);border:1px solid var(--line);border-radius:12px;padding:5px;margin-bottom:14px;flex-wrap:wrap}
.seg button{flex:1;min-width:64px;background:none;border:0;color:var(--muted);font:inherit;font-weight:600;
  padding:9px 8px;border-radius:9px;cursor:pointer;font-size:.85rem}
.seg button.active{background:var(--card2);color:var(--ink)}

/* toggle switch (label) */
.switch{display:inline-flex;align-items:center;gap:7px;font-size:.8rem;color:var(--muted);cursor:pointer}
.switch input{appearance:none;width:34px;height:20px;background:var(--card2);border:1px solid var(--line);
  border-radius:999px;position:relative;transition:background .15s;flex:0 0 auto}
.switch input:checked{background:var(--accent)}
.switch input::after{content:"";position:absolute;top:2px;left:2px;width:14px;height:14px;border-radius:50%;
  background:#fff;transition:transform .15s}
.switch input:checked::after{transform:translateX(14px)}

/* stat grid */
.statgrid{display:grid;grid-template-columns:repeat(4,1fr);gap:8px;margin:14px 0}
.statgrid .stat{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:10px 4px}
.statgrid .stat b{font-size:1.05rem}
.statgrid .stat small{font-size:.66rem}

/* last-layer diagrams (OLL/PLL flat view) */
.ll-wrap{--c:20px;display:inline-grid;grid-template-columns:8px repeat(3,var(--c)) 8px;grid-template-rows:8px repeat(3,var(--c)) 8px;gap:2px}
.ll-wrap i{border-radius:2px;background:#26314f}
.ll-wrap i.y{background:var(--wD)}
.ll-wrap i.t{background:#141c38}       /* empty top-face cell (not oriented) */
.ll-wrap i.wU{background:var(--wU)} .ll-wrap i.wR{background:var(--wR)} .ll-wrap i.wL{background:var(--wL)}
.ll-wrap i.wF{background:var(--wF)} .ll-wrap i.wB{background:var(--wB)} .ll-wrap i.wD{background:var(--wD)}
.ll-wrap i.blank{background:transparent}
.ll-card{display:flex;flex-direction:column;align-items:center;gap:6px;background:var(--card);
  border:1px solid var(--line);border-radius:12px;padding:12px 6px;cursor:pointer;transition:border-color .15s}
.ll-card:hover{border-color:var(--accent)}
.ll-card .nm{font-size:.72rem;color:var(--muted);text-align:center}
.ll-card .mv{font-family:ui-monospace,monospace;font-size:.62rem;color:var(--muted);text-align:center;word-break:break-word;line-height:1.3}
.ll-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(96px,1fr));gap:10px;margin-bottom:16px}
.svg-arrows{position:absolute;inset:0;pointer-events:none}
.pll-diagram{position:relative;display:inline-block}

/* trainer */
.train-face{margin:8px 0}
.rate{display:grid;grid-template-columns:repeat(3,1fr);gap:8px;margin-top:12px}
.rate .btn{padding:14px 0}
.big-alg{font-family:ui-monospace,monospace;font-size:1.2rem;font-weight:700;text-align:center;
  letter-spacing:.04em;margin:12px 0;word-spacing:.15em}