/* 课后练习 — visual language from HFL Teaching Hub (paper, plum, gold, tiles). */
:root{
  --ink:#2E2443;
  --muted:#6F6689;
  --plum:#5B45A8;
  --plum-2:#7A63CC;
  --lilac:#EFEAFE;
  --line:#E4DEF3;
  --paper:#FFFCF5;
  --card:#FFFFFF;
  --gold:#FFC93C;
  --gold-deep:#E9A11E;
  --rose:#E2559A;
  --ok:#2E9E6A;
  --warn:#C9761F;
  --bad:#D2445B;
  --f-display:"Baloo 2","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --f-body:"Atkinson Hyperlegible","PingFang SC","Microsoft YaHei","Noto Sans SC",system-ui,sans-serif;
  --f-letter:"Andika","Comic Sans MS",sans-serif;
  --radius:14px;
  color-scheme:light;
}
*{box-sizing:border-box}
[hidden]{display:none!important}
html,body{margin:0;min-height:100%}
body{background:var(--paper);color:var(--ink);font-family:var(--f-body);font-size:16px;line-height:1.5;-webkit-font-smoothing:antialiased;-webkit-tap-highlight-color:transparent}
a{color:var(--plum)}
h1,h2,h3{font-family:var(--f-display);line-height:1.15;margin:0;text-wrap:balance}
.cn{font-family:"PingFang SC","Microsoft YaHei","Noto Sans SC",sans-serif}
.wrap{max-width:1120px;margin:0 auto;padding-left:max(20px,env(safe-area-inset-left,0px));padding-right:max(20px,env(safe-area-inset-right,0px))}

.btn{appearance:none;border:0;cursor:pointer;font:600 15px/1 var(--f-body);display:inline-flex;align-items:center;justify-content:center;gap:8px;
  padding:12px 18px;min-height:44px;border-radius:999px;background:var(--plum);color:#fff;text-decoration:none;box-shadow:0 3px 0 #3F2F7E;transition:transform .1s,background .15s;touch-action:manipulation}
.btn:hover{background:var(--plum-2)}
.btn:active{transform:translateY(2px);box-shadow:0 1px 0 #3F2F7E}
.btn:focus-visible,.input:focus-visible{outline:3px solid var(--gold);outline-offset:2px}
.btn.gold{background:linear-gradient(#FFE07A,var(--gold));color:var(--ink);box-shadow:0 3px 0 var(--gold-deep)}
.btn.gold:hover{filter:brightness(1.02)}
.btn.ghost{background:transparent;color:var(--plum);box-shadow:inset 0 0 0 1.5px var(--line)}
.btn.ghost:hover{background:var(--lilac)}

.topbar{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:env(safe-area-inset-top,0px);z-index:5}
.topbar .wrap{display:flex;align-items:center;gap:16px;min-height:66px;flex-wrap:wrap;padding-block:8px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--ink);margin-right:auto}
.brand-mark{width:38px;height:38px;flex:none}
.brand b{font-family:var(--f-display);font-weight:800;font-size:21px;color:var(--plum);display:block;line-height:1}

.hero{padding-block:36px 22px;display:flex;align-items:flex-end;justify-content:space-between;gap:20px;flex-wrap:wrap}
.hero h1{font-size:clamp(30px,4vw,42px);font-weight:800}
.hero p{margin:6px 0 0;color:var(--muted)}
.back{display:inline-flex;align-items:center;gap:6px;margin:0 0 10px;padding:0;border:0;background:none;color:var(--plum);font:700 14px var(--f-body);cursor:pointer;text-decoration:none;min-height:44px;touch-action:manipulation}
.back:hover{text-decoration:underline}
.back:focus-visible{outline:3px solid var(--gold);outline-offset:3px}

.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(270px,1fr));gap:20px;padding-bottom:56px}
.game{background:var(--card);border:1px solid var(--line);border-radius:18px;overflow:hidden;display:flex;flex-direction:column;text-decoration:none;color:inherit;transition:transform .15s,box-shadow .15s}
.game:hover{transform:translateY(-3px);box-shadow:0 12px 28px rgba(46,36,67,.14)}
.game:focus-visible{outline:3px solid var(--gold);outline-offset:3px}
.cover{aspect-ratio:4/3;max-width:100%;position:relative;display:grid;place-items:center;border-bottom:1px solid var(--line)}
.cover .ls{display:flex;gap:10px}
.cover .ls span{width:54px;height:58px;border-radius:13px;background:#fff;border:3px solid var(--ink);display:grid;place-items:center;font:700 32px var(--f-letter);color:var(--plum);box-shadow:0 4px 0 rgba(46,36,67,.25)}
.cover .ls span:nth-child(odd){transform:rotate(-6deg)}
.cover .ls span:nth-child(even){transform:rotate(5deg) translateY(6px)}
.cover .ls span:nth-child(2){background:#FFE07A}
.cover .ls span:nth-child(3){background:#FFC2D6}
.body{padding:16px 18px 18px;display:grid;gap:8px;flex:1}
.body h2{font-size:21px;font-weight:800}
.play{display:flex;align-items:center;justify-content:center;gap:8px;margin:0 18px 18px;padding:11px;border-radius:999px;background:var(--plum);color:#fff;font-weight:700;font-size:15px}
.game:hover .play{background:var(--plum-2)}

.teacher-hero{padding-block:22px 16px}
.teacher-hero .tools{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.stage{
  width:100%;
  height:calc(100dvh - 13.5rem);
  min-height:28rem;
  margin:0 0 max(24px, env(safe-area-inset-bottom, 0px));
  background:#1b1446;
  border:1px solid var(--line);
  border-radius:18px;
  overflow:hidden;
  box-shadow:0 12px 28px rgba(46,36,67,.12);
}
.stage iframe{width:100%;height:100%;border:0;display:block;background:#1b1446}

.toast{position:fixed;left:50%;bottom:max(24px,env(safe-area-inset-bottom,0px));transform:translate(-50%,20px);background:var(--ink);color:#fff;padding:12px 18px;border-radius:12px;font-size:14px;opacity:0;pointer-events:none;transition:.25s;z-index:60;max-width:calc(100% - 32px)}
.toast.show{opacity:1;transform:translate(-50%,0)}

.miss{padding:48px 0 72px}
.miss h1{font-size:clamp(28px,4vw,40px);font-weight:800;margin-bottom:10px}
.miss p{margin:0;color:var(--muted)}

@media (max-width:600px){
  .hero{padding-block:24px 18px}
  .stage{height:calc(100dvh - 12.25rem);min-height:24rem;border-radius:14px}
  .teacher-hero .btn{width:100%}
}

@media (prefers-reduced-motion: reduce){*{transition:none!important;animation:none!important}}