/* Layout: one column up to tablet width — header with stars, screen content, fixed bottom tab bar.
   Game and editor screens use a big expression line over a large on-screen keypad. */
:root{
  --bg:#FFF8EC; --surface:#FFFFFF; --surface-2:#F6EEDD; --ink:#1E2333; --muted:#6B6F80; --line:#EADFC8;
  --accent:#3D5AFE; --accent-ink:#FFFFFF; --accent-soft:#E3E8FF;
  --ok:#21A35B; --ok-soft:#DDF5E7; --bad:#E5484D; --bad-soft:#FDE4E4; --peek:#2F7FD8; --peek-soft:#E1EEFC;
  --star:#F5A524;
  --add:#21A35B; --sub:#F08C00; --mul:#8B5CF6; --div:#0FA3B1;
  --shadow:0 1px 2px rgba(30,35,51,.06),0 8px 24px rgba(30,35,51,.08);
  --key:#FFFFFF; --key-edge:#E6DAC2;
  --f:"Nunito",-apple-system,system-ui,"Segoe UI",Roboto,sans-serif;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --bg:#14161F; --surface:#1D202C; --surface-2:#262A38; --ink:#ECEEF6; --muted:#9CA1B5; --line:#2F3445;
  --accent:#8C9EFF; --accent-ink:#10132A; --accent-soft:#272E52;
  --ok:#4CD487; --ok-soft:#183A28; --bad:#FF7A7E; --bad-soft:#41202A; --peek:#6FB0FF; --peek-soft:#1C3150;
  --star:#FFC24D;
  --add:#4CD487; --sub:#FFAA3B; --mul:#B39BFF; --div:#4FD1DD;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 8px 24px rgba(0,0,0,.35);
  --key:#262A38; --key-edge:#13151D; color-scheme:dark}}
:root[data-theme="dark"]{
  --bg:#14161F; --surface:#1D202C; --surface-2:#262A38; --ink:#ECEEF6; --muted:#9CA1B5; --line:#2F3445;
  --accent:#8C9EFF; --accent-ink:#10132A; --accent-soft:#272E52;
  --ok:#4CD487; --ok-soft:#183A28; --bad:#FF7A7E; --bad-soft:#41202A; --peek:#6FB0FF; --peek-soft:#1C3150;
  --star:#FFC24D;
  --add:#4CD487; --sub:#FFAA3B; --mul:#B39BFF; --div:#4FD1DD;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 8px 24px rgba(0,0,0,.35);
  --key:#262A38; --key-edge:#13151D; color-scheme:dark}
*{box-sizing:border-box}
[hidden]{display:none!important}
html{-webkit-text-size-adjust:100%}
html,body{background:var(--bg)}
body{margin:0;padding-top:env(safe-area-inset-top,0px);color:var(--ink);font-family:var(--f);font-size:17px;line-height:1.4;font-weight:500;-webkit-tap-highlight-color:transparent}
button,input,textarea,select{font:inherit;color:inherit}
button{cursor:pointer;-webkit-user-select:none;user-select:none;touch-action:manipulation}
:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
.wrap{max-width:720px;margin:0 auto;padding-inline:16px;padding-block:0 calc(96px + env(safe-area-inset-bottom,0px))}
body.ingame .wrap{padding-bottom:16px}
.loading{color:var(--muted);text-align:center;margin-top:30vh}
h1,h2,h3{margin:0;font-weight:900;line-height:1.15;text-wrap:balance}
h2{font-size:20px}
h3{font-size:17px}
.muted{color:var(--muted)}
.small{font-size:14px}
.num{font-variant-numeric:tabular-nums}

/* header */
header.top{position:sticky;top:0;z-index:5;background:var(--bg);padding-block:12px 10px;display:flex;align-items:center;gap:10px;min-height:60px}
.brand{font-weight:900;font-size:20px;letter-spacing:-.01em;color:var(--accent);display:flex;align-items:center;gap:8px}
.brand .logo{width:30px;height:30px;border-radius:9px;background:var(--accent);color:var(--accent-ink);display:grid;place-items:center;font-size:18px;line-height:1}
.badges{margin-left:auto;display:flex;gap:6px}
.badge{display:flex;align-items:center;gap:5px;background:var(--surface);border:1px solid var(--line);border-radius:999px;padding:5px 11px;font-weight:800;font-size:15px;font-variant-numeric:tabular-nums}
.badge .ic{font-size:15px}
.demo-tag{font-size:12px;font-weight:800;color:#8A5A00;background:#FFE7B3;border-radius:6px;padding:2px 7px}
.iconbtn{width:44px;height:44px;border-radius:14px;border:1px solid var(--line);background:var(--surface);display:grid;place-items:center;font-size:20px;flex:none}

/* bottom bar */
nav.bar{position:fixed;left:0;right:0;bottom:0;z-index:10;background:color-mix(in srgb,var(--bg) 88%,transparent);backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);border-top:1px solid var(--line);padding:8px 12px calc(8px + env(safe-area-inset-bottom,0px))}
nav.bar .tabs{max-width:720px;margin:0 auto;display:flex;gap:6px}
.tab{flex:1;border:0;background:transparent;border-radius:14px;padding:8px 4px;display:flex;flex-direction:column;align-items:center;gap:2px;font-weight:800;font-size:13px;color:var(--muted)}
.tab .ic{font-size:22px;line-height:1}
.tab[aria-selected="true"]{background:var(--accent-soft);color:var(--accent)}

/* cards and controls */
.card{background:var(--surface);border:1px solid var(--line);border-radius:22px;padding:18px;box-shadow:var(--shadow);margin-bottom:14px}
.card h2{margin-bottom:12px}
.hello{margin:6px 0 16px}
.hello h1{font-size:28px}
.hello p{margin:4px 0 0;color:var(--muted)}
.label{font-size:13px;font-weight:800;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);margin:16px 0 8px}
.label:first-of-type{margin-top:4px}
.row{display:flex;gap:8px;flex-wrap:wrap}
.chip{border:2px solid var(--line);background:var(--surface);border-radius:16px;padding:10px 16px;font-weight:800;font-size:16px;min-height:48px;display:inline-flex;align-items:center;gap:8px}
.chip[aria-pressed="true"]{border-color:var(--accent);background:var(--accent-soft);color:var(--accent)}
.opchip{width:64px;height:64px;justify-content:center;font-size:30px;padding:0;border-radius:18px}
.opchip[aria-pressed="true"]{color:#fff;border-color:transparent}
.opchip.add[aria-pressed="true"]{background:var(--add)} .opchip.sub[aria-pressed="true"]{background:var(--sub)}
.opchip.mul[aria-pressed="true"]{background:var(--mul)} .opchip.div[aria-pressed="true"]{background:var(--div)}
.levels{display:grid;grid-template-columns:repeat(5,1fr);gap:6px}
.level{border:2px solid var(--line);background:var(--surface);border-radius:16px;padding:8px 2px;display:flex;flex-direction:column;align-items:center;gap:2px;min-height:64px;justify-content:center}
.level .stars{color:var(--star);font-size:13px;letter-spacing:-1px;line-height:1}
.level .t{font-weight:800;font-size:14px;white-space:nowrap}
.level[aria-pressed="true"]{border-color:var(--accent);background:var(--accent-soft);color:var(--accent)}
.leveldesc{font-size:14px;color:var(--muted);margin-top:8px}
.btn{border:0;border-radius:18px;padding:14px 20px;font-weight:900;font-size:18px;min-height:56px;background:var(--surface-2);color:var(--ink);display:inline-flex;align-items:center;justify-content:center;gap:8px}
.btn.primary{background:var(--accent);color:var(--accent-ink);box-shadow:0 4px 0 color-mix(in srgb,var(--accent) 60%,#000)}
.btn.primary:active{transform:translateY(2px);box-shadow:0 2px 0 color-mix(in srgb,var(--accent) 60%,#000)}
.btn.ok{background:var(--ok);color:#fff}
.btn.peek{background:var(--peek-soft);color:var(--peek)}
.btn.ghost{background:transparent;border:2px solid var(--line)}
.btn.small{min-height:44px;font-size:16px;padding:8px 14px;border-radius:14px}
.btn.wide{width:100%}
.btn:disabled{opacity:.45;cursor:default;box-shadow:none}
.gobtn{margin-top:18px}
.shortcuts{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-bottom:14px}
.shortcut{border:1px solid var(--line);background:var(--surface);border-radius:20px;padding:14px;text-align:left;display:flex;flex-direction:column;gap:2px;box-shadow:var(--shadow)}
.shortcut .ic{font-size:26px}
.shortcut b{font-weight:900}
.shortcut span{font-size:14px;color:var(--muted)}
.shortcut:disabled{opacity:.55;cursor:default}
.task{display:flex;align-items:center;gap:12px;border:2px solid var(--star);background:color-mix(in srgb,var(--star) 12%,var(--surface));border-radius:20px;padding:14px;margin-bottom:12px}
.task .ic{font-size:30px}
.task .body{flex:1;min-width:0}
.task b{display:block;font-weight:900}
.task span{font-size:14px;color:var(--muted)}
.empty{color:var(--muted);font-size:15px;text-align:center;padding:12px}
.error{color:var(--bad);font-weight:700;font-size:15px;min-height:1.4em}
.field{display:block;margin-bottom:12px}
.field span{display:block;font-size:14px;font-weight:700;color:var(--muted);margin-bottom:4px}
.field input,.field textarea{width:100%;border:2px solid var(--line);background:var(--surface);border-radius:14px;padding:12px;font-size:18px}
.field textarea{min-height:150px;font-variant-numeric:tabular-nums;line-height:1.6}
.toggle{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:12px 0;border-top:1px solid var(--line)}
.toggle:first-child{border-top:0}
.toggle input{width:24px;height:24px;accent-color:var(--accent)}

/* login */
.login{max-width:380px;margin:8vh auto 0}
.login .hero{font-size:56px;text-align:center;margin-bottom:6px}
.login h1{text-align:center;font-size:30px;margin-bottom:6px}
.login p{text-align:center;color:var(--muted);margin:0 0 20px}

/* game */
.gamebar{display:flex;align-items:center;gap:10px;margin:4px 0 10px}
.progress{flex:1;height:14px;border-radius:999px;background:var(--surface-2);overflow:hidden}
.progress i{display:block;height:100%;background:var(--accent);border-radius:999px;transition:width .3s}
.progress.timer i{background:var(--star);transition:width 1s linear}
.counter{font-weight:900;font-variant-numeric:tabular-nums;min-width:56px;text-align:right}
.stage{background:var(--surface);border:1px solid var(--line);border-radius:28px;box-shadow:var(--shadow);padding:22px 14px 18px;text-align:center;position:relative}
.expr{font-weight:900;font-variant-numeric:tabular-nums;line-height:1.15;display:flex;flex-wrap:wrap;justify-content:center;align-items:center;gap:.25em;min-height:1.4em;letter-spacing:-.01em}
.expr .op{color:var(--muted)}
.expr .o-add{color:var(--add)} .expr .o-sub{color:var(--sub)} .expr .o-mul{color:var(--mul)} .expr .o-div{color:var(--div)}
.box{display:inline-flex;align-items:center;justify-content:center;min-width:1.6em;padding:0 .2em;height:1.3em;border-radius:.22em;border:.07em solid var(--accent);background:var(--accent-soft);color:var(--accent)}
.box.blank::after{content:"";width:.06em;height:.8em;background:currentColor;animation:blink 1s steps(1) infinite}
.box.right{border-color:var(--ok);background:var(--ok-soft);color:var(--ok)}
.box.wrong{border-color:var(--bad);background:var(--bad-soft);color:var(--bad);animation:shake .35s}
.box.peek{border-color:var(--peek);background:var(--peek-soft);color:var(--peek)}
@keyframes blink{50%{opacity:0}}
@keyframes shake{20%,60%{transform:translateX(-6px)}40%,80%{transform:translateX(6px)}}
.feedback{min-height:32px;margin-top:12px;font-weight:900;font-size:20px}
.feedback.right{color:var(--ok)} .feedback.wrong{color:var(--bad)} .feedback.peek{color:var(--peek)}
.explain{margin-top:10px;background:var(--peek-soft);border-radius:18px;padding:12px 14px;text-align:left}
.explain p{margin:4px 0;font-size:18px;font-weight:700;font-variant-numeric:tabular-nums}
.explain p:first-child{margin-top:0}
.dots{display:grid;grid-template-columns:repeat(10,1fr);gap:6px;max-width:340px;margin:10px auto 6px}
.dots i{aspect-ratio:1;border-radius:50%;background:var(--peek);position:relative}
.dots i:nth-child(10n+5){margin-right:6px}
.dots i.b{background:var(--star)}
.dots i.off{background:transparent;border:2px dashed var(--muted);opacity:.5}
.dots i.x::after{content:"";position:absolute;inset:-3px;background:linear-gradient(45deg,transparent 45%,var(--bad) 45%,var(--bad) 55%,transparent 55%)}
.dots i.x{opacity:.55}
.gameactions{display:flex;gap:8px;margin-top:12px}
.gameactions .btn{flex:1}
.pulse{animation:pulse 1.2s ease-in-out infinite}
@keyframes pulse{50%{transform:scale(1.04)}}

/* keypad */
.keypad{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-top:14px;max-width:440px;margin-inline:auto}
.keypad.ops{grid-template-columns:repeat(5,1fr);max-width:560px;gap:8px}
.key{border:0;background:var(--key);border-radius:18px;font-weight:900;font-size:30px;min-height:64px;box-shadow:0 3px 0 var(--key-edge),0 0 0 1px var(--line) inset;font-variant-numeric:tabular-nums}
.key:active{transform:translateY(2px);box-shadow:0 1px 0 var(--key-edge),0 0 0 1px var(--line) inset}
.keypad.ops .key{min-height:58px;font-size:26px}
.key.op{color:#fff;box-shadow:0 3px 0 color-mix(in srgb,currentColor 0%,#0003)}
.key.k-add{background:var(--add)} .key.k-sub{background:var(--sub)} .key.k-mul{background:var(--mul)} .key.k-div{background:var(--div)}
.key.fn{background:var(--surface-2);font-size:22px}
.key.go{background:var(--ok);color:#fff;box-shadow:0 3px 0 color-mix(in srgb,var(--ok) 55%,#000)}
.key:disabled{opacity:.4}

/* result */
.result{text-align:center}
.result .big{font-size:64px;line-height:1;margin:8px 0}
.result h1{font-size:30px}
.result .score{font-size:20px;font-weight:800;margin:8px 0 16px}
.result .record{display:inline-block;background:var(--star);color:#3A2600;border-radius:999px;padding:4px 14px;font-weight:900;margin-bottom:10px}
.list{display:flex;flex-direction:column;gap:6px;text-align:left}
.li{display:flex;align-items:center;gap:10px;background:var(--surface-2);border-radius:14px;padding:10px 12px;font-variant-numeric:tabular-nums}
.li .mark{width:30px;height:30px;border-radius:10px;display:grid;place-items:center;font-weight:900;flex:none;color:#fff}
.li .mark.ok{background:var(--ok)} .li .mark.again{background:var(--sub)} .li .mark.peek{background:var(--peek)} .li .mark.miss{background:var(--bad)}
.li .q{flex:1;font-weight:800;font-size:18px;overflow-wrap:anywhere}
.li .given{font-size:14px;color:var(--muted)}
.li button{flex:none}
.resultactions{display:flex;flex-direction:column;gap:8px;margin-top:16px}

/* editor */
.screen{background:var(--surface);border:1px solid var(--line);border-radius:24px;padding:16px;min-height:96px;display:flex;flex-direction:column;justify-content:center;box-shadow:var(--shadow)}
.screen .typed{font-weight:900;font-size:clamp(28px,8vw,44px);font-variant-numeric:tabular-nums;text-align:right;overflow-wrap:anywhere;line-height:1.15}
.screen .typed .ph{color:var(--muted);font-weight:700;font-size:20px}
.screen .typed .caret{display:inline-block;width:3px;height:.9em;background:var(--accent);vertical-align:-.1em;margin-left:2px;animation:blink 1s steps(1) infinite}
.screen .hint{font-size:15px;color:var(--muted);text-align:right;min-height:1.3em;margin-top:4px}
.verdict{border-radius:18px;padding:14px;margin-top:12px;font-weight:800;font-size:18px}
.verdict.right{background:var(--ok-soft);color:var(--ok)}
.verdict.wrong{background:var(--bad-soft);color:var(--bad)}
.verdict.info{background:var(--peek-soft);color:var(--peek)}
.verdict.err{background:var(--surface-2);color:var(--muted)}
.verdict .ans{font-size:30px;font-weight:900;display:block;color:var(--ink);font-variant-numeric:tabular-nums;margin-top:2px}
.verdict .explain{background:transparent;padding:6px 0 0;color:var(--ink)}
.editactions{display:grid;grid-template-columns:1fr 1fr;gap:8px;margin-top:12px}
.screen+.gameactions,.stage+.gameactions{margin-bottom:4px}
.editactions .btn{font-size:16px;padding:10px 8px}

/* progress */
.tiles{display:grid;grid-template-columns:repeat(4,1fr);gap:8px;margin-bottom:14px}
.tile{background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:12px 8px;text-align:center;box-shadow:var(--shadow)}
.tile .v{font-size:28px;font-weight:900;font-variant-numeric:tabular-nums;line-height:1.1}
.tile .k{font-size:13px;color:var(--muted);font-weight:700}
.bars{display:grid;grid-template-columns:repeat(14,1fr);gap:4px;align-items:end;height:110px}
.bars .col{display:flex;flex-direction:column;justify-content:flex-end;height:100%;border-radius:6px;background:var(--surface-2);overflow:hidden}
.bars .col i{display:block;background:var(--accent)}
.bars .col i.miss{background:color-mix(in srgb,var(--accent) 35%,var(--surface-2))}
.bars-x{display:grid;grid-template-columns:repeat(14,1fr);gap:4px;font-size:11px;color:var(--muted);text-align:center;margin-top:4px;font-variant-numeric:tabular-nums}
.oprow{display:grid;grid-template-columns:40px 1fr 64px;gap:10px;align-items:center;margin:8px 0}
.oprow .sg{width:40px;height:40px;border-radius:12px;color:#fff;font-weight:900;font-size:22px;display:grid;place-items:center}
.oprow .meter{height:12px;border-radius:999px;background:var(--surface-2);overflow:hidden}
.oprow .meter i{display:block;height:100%;border-radius:999px}
.oprow .pc{font-weight:900;text-align:right;font-variant-numeric:tabular-nums}
.oprow .sub{grid-column:2/4;font-size:13px;color:var(--muted);margin-top:-6px}
.bg-add{background:var(--add)} .bg-sub{background:var(--sub)} .bg-mul{background:var(--mul)} .bg-div{background:var(--div)} .bg-mix{background:var(--accent)}
.chips{display:flex;flex-wrap:wrap;gap:6px}
.qchip{border:1px solid var(--line);background:var(--surface-2);border-radius:12px;padding:8px 12px;font-weight:800;font-variant-numeric:tabular-nums}

/* parent */
.kidhead{display:flex;align-items:center;gap:12px;margin-bottom:12px}
.kidhead .av{width:48px;height:48px;border-radius:16px;background:var(--accent);color:var(--accent-ink);display:grid;place-items:center;font-weight:900;font-size:22px}
.kidhead h2{margin:0}
.kidhead .sp{flex:1}
.assign{border:1px solid var(--line);border-radius:16px;padding:12px;margin-top:8px}
.assign .h{display:flex;align-items:center;gap:8px;justify-content:space-between}
.assign .h b{font-weight:900}
.status{font-size:13px;font-weight:800;border-radius:999px;padding:3px 10px;white-space:nowrap}
.status.open{background:#FFE7B3;color:#7A4D00}
.status.done{background:var(--ok-soft);color:var(--ok)}
.preview{display:flex;flex-direction:column;gap:4px;margin:6px 0 12px;font-variant-numeric:tabular-nums}
.preview div{display:flex;justify-content:space-between;gap:10px;font-size:15px;padding:4px 8px;border-radius:8px;background:var(--surface-2)}
.preview .bad{background:var(--bad-soft);color:var(--bad)}

/* sheet */
.sheet-bg{position:fixed;inset:0;z-index:20;background:rgba(10,12,20,.45);display:flex;align-items:flex-end;justify-content:center}
.sheet{width:100%;max-width:720px;max-height:92vh;overflow:auto;background:var(--bg);border-radius:26px 26px 0 0;padding:18px 16px calc(18px + env(safe-area-inset-bottom,0px))}
.sheet .sh{display:flex;align-items:center;gap:10px;margin-bottom:12px}
.sheet .sh h2{flex:1}

/* confetti */
#fx{position:fixed;inset:0;pointer-events:none;z-index:30;overflow:hidden}
#fx i{position:absolute;top:-20px;width:10px;height:14px;border-radius:3px;animation:fall 1.8s ease-in forwards}
@keyframes fall{to{transform:translateY(110vh) rotate(720deg);opacity:.6}}
.pop{animation:pop .35s ease-out}
@keyframes pop{0%{transform:scale(.7)}70%{transform:scale(1.12)}100%{transform:scale(1)}}
@media (prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}#fx{display:none}}

@media (max-width:420px){
  .opchip{width:58px;height:58px;font-size:26px}
  .level .t{font-size:12px}
  .key{min-height:58px;font-size:26px}
  .tiles{grid-template-columns:repeat(2,1fr)}
  .badge{padding:4px 9px;font-size:14px}
}
@media (min-width:700px){
  .key{min-height:72px}
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]) .opchip[aria-pressed="true"],:root:not([data-theme="light"]) .key.op,:root:not([data-theme="light"]) .oprow .sg{color:#10132A}}
:root[data-theme="dark"] .opchip[aria-pressed="true"],:root[data-theme="dark"] .key.op,:root[data-theme="dark"] .oprow .sg{color:#10132A}