/* Giao diện chung: trời sao xanh đậm + đảo nổi, khối bo tròn màu kem (tham khảo SeedStep), nút dày kiểu Roblox */
:root{
  --troi:#0d1633; --troi2:#1b2a5c; --chu-nen:#fdf8ec; --mo-nen:#aab8e6;
  --the:#fdf8ec; --the2:#eef6e4; --chu:#1d2b4f; --mo:#5d6a8f; --vien:#c9d9b8;
  --bac-ha:#7fe0a8; --la:#3fae6a; --la-dam:#2c7a4b; --cam:#ff8a3d; --cam-dam:#d8661c;
  --xanh:#4c8dff; --vang:#ffd23f; --do:#ff5d5d;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){ --troi:#0a1129; --troi2:#16224d; }
}
:root[data-theme="dark"]{ --troi:#0a1129; --troi2:#16224d; }
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;color:var(--chu-nen);font-family:"Baloo 2",system-ui,sans-serif;font-size:18px}
body{min-height:100vh;user-select:none;-webkit-user-select:none;background-color:var(--troi);
  background-image:
    radial-gradient(2px 2px at 12% 18%,#fff8,transparent 60%),radial-gradient(2px 2px at 78% 12%,#fff9,transparent 60%),
    radial-gradient(1.5px 1.5px at 40% 70%,#fff7,transparent 60%),radial-gradient(2px 2px at 88% 64%,#fff8,transparent 60%),
    radial-gradient(1.5px 1.5px at 25% 88%,#fff6,transparent 60%),radial-gradient(1.5px 1.5px at 60% 35%,#fff6,transparent 60%),
    radial-gradient(1200px 600px at 80% -10%,var(--troi2),transparent 70%);
  background-attachment:fixed}
h1,h2,h3{margin:0;line-height:1.15}
button{font:inherit;cursor:pointer;border:0;border-radius:18px;box-shadow:0 6px 0 var(--vien);
  background:var(--the);color:var(--chu);padding:10px 18px;font-weight:800;transition:transform .06s}
button:active{transform:translateY(5px);box-shadow:0 1px 0 var(--vien)}
button:disabled{opacity:.45;cursor:not-allowed}
.btn-cam{background:var(--cam);color:#fff;box-shadow:0 6px 0 var(--cam-dam)}
.btn-la{background:var(--la);color:#fff;box-shadow:0 6px 0 var(--la-dam)}
.btn-xanh{background:var(--xanh);color:#fff;box-shadow:0 6px 0 #2a5fc4}
.btn-do{background:var(--do);color:#fff;box-shadow:0 6px 0 #c23b3b}
.the{background:var(--the);color:var(--chu);border-radius:24px;box-shadow:0 8px 0 var(--vien),0 18px 40px #0006;padding:16px}
.hud{position:sticky;top:0;z-index:20;display:flex;gap:8px;align-items:center;padding:10px 16px;
  background:color-mix(in srgb,var(--troi) 88%,transparent);backdrop-filter:blur(6px);flex-wrap:wrap}
.hud .chip{display:flex;align-items:center;gap:6px;background:var(--the);color:var(--chu);
  border-radius:999px;padding:2px 14px;font-weight:800;box-shadow:0 4px 0 var(--vien)}
.hud .ten{font-weight:800;margin-right:auto;display:flex;align-items:center;gap:8px;font-size:1.1rem}
.hud a{color:var(--bac-ha);text-decoration:none;font-weight:800}
.mau-dot{width:30px;height:30px;border-radius:10px;display:inline-grid;place-items:center;font-size:18px}

/* Hộp câu hỏi */
.quiz-nen{position:fixed;inset:0;background:rgba(5,10,30,.78);z-index:100;display:flex;align-items:center;justify-content:center;padding:16px}
.quiz{width:min(580px,100%);max-height:94vh;overflow:auto}
.quiz .dau{display:flex;justify-content:space-between;align-items:center;font-weight:800;color:var(--mo);gap:8px}
.quiz .cau{font-size:1.45rem;font-weight:800;margin:10px 0 6px;line-height:1.35}
.quiz .hinh{font-size:2.8rem;text-align:center;line-height:1.25;margin:6px 0;word-break:break-word;white-space:pre-line}
.quiz .dap{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-top:14px}
.quiz .dap button{font-size:1.25rem;min-height:64px;white-space:normal;line-height:1.25;background:var(--the2)}
.quiz .dap button.dung{background:var(--la);color:#fff;box-shadow:0 6px 0 var(--la-dam)}
.quiz .dap button.sai{background:var(--do);color:#fff;box-shadow:0 6px 0 #c23b3b}
.quiz .giai{margin-top:14px;padding:10px 14px;border-radius:14px;background:#e3f0ff;font-weight:600}
.quiz .thanh{height:12px;border-radius:99px;overflow:hidden;margin-top:6px;background:#e5e0cf}
.quiz .thanh i{display:block;height:100%;background:var(--bac-ha);transition:width .3s}
.tuoi5 .quiz .cau{font-size:1.7rem}.tuoi5 .quiz .dap button{font-size:1.7rem;min-height:84px}
.loa{border-radius:999px;padding:6px 14px}

.toast{position:fixed;left:50%;top:76px;transform:translateX(-50%);z-index:200;background:var(--vang);color:#1d2b4f;
  border-radius:16px;padding:8px 18px;font-weight:800;box-shadow:0 5px 0 #c79f10;animation:bay 1.9s forwards;pointer-events:none;text-align:center;max-width:90vw}
@keyframes bay{0%{opacity:0;transform:translate(-50%,10px)}12%{opacity:1;transform:translate(-50%,0)}80%{opacity:1}100%{opacity:0;transform:translate(-50%,-20px)}}
@media (max-width:420px){.quiz .dap{grid-template-columns:1fr}}