:root {
  --green: #0E4D3A; --green-2: #16684f; --red: #C8102E; --ink: #1b1b1b; --grey: #5a5f66;
  --line: #dfe3e1; --bg: #f4f5f2; --card: #ffffff; --ok: #1d7a46; --ko: #b3261e;
}
@media (prefers-color-scheme: dark) {
  :root { --ink: #ecefed; --grey: #a7aeab; --line: #2c3431; --bg: #111614; --card: #1a201e; --ok: #4cc27f; --ko: #ff8a80; }
}
* { box-sizing: border-box; }
html, body { margin: 0; background: var(--bg); color: var(--ink);
  font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", "Noto Sans Bengali", "PingFang SC", "Microsoft YaHei", sans-serif; }
.bar { position: sticky; top: 0; z-index: 2; display: flex; justify-content: space-between; align-items: center;
  padding: 12px 16px; background: var(--green); color: #fff; }
.bar a { color: #fff; text-decoration: none; font-weight: 600; }
.lang { font-size: 14px; border: 1px solid rgba(255,255,255,.5); border-radius: 999px; padding: 2px 12px; }
main { max-width: 680px; margin: 0 auto; padding: 16px; }
h1 { font-size: 22px; margin: 4px 0 12px; }
h2 { font-size: 17px; margin: 20px 0 8px; }
p.sub { color: var(--grey); margin: 0 0 16px; }
.btn { display: block; width: 100%; padding: 14px 16px; margin: 8px 0; border-radius: 12px; border: 1px solid var(--line);
  background: var(--card); color: var(--ink); font: inherit; font-weight: 600; text-align: left; text-decoration: none; cursor: pointer; }
.btn.primary { background: var(--green); color: #fff; border-color: var(--green); text-align: center; }
.btn small { display: block; font-weight: 400; color: var(--grey); }
.btn.primary small { color: #d6eee4; }
.row { display: flex; gap: 8px; }
.row .btn { text-align: center; }
.chap { display: flex; justify-content: space-between; gap: 12px; align-items: center; }
.chap .meta { color: var(--grey); font-size: 13px; white-space: nowrap; }
.chap .lock { color: var(--red); font-size: 13px; font-weight: 600; white-space: nowrap; }
.bar-prog { height: 4px; background: var(--line); border-radius: 2px; margin-top: 6px; overflow: hidden; }
.bar-prog i { display: block; height: 100%; background: var(--green-2); }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 16px; margin: 8px 0 12px; }
.card img { display: block; max-width: 100%; max-height: 220px; margin: 0 auto 12px; background: #fff; border-radius: 6px; }
.qnum { color: var(--grey); font-size: 13px; display: flex; justify-content: space-between; }
.it { font-size: 19px; line-height: 1.45; margin: 8px 0; }
.tr { color: var(--grey); font-size: 16px; border-top: 1px dashed var(--line); padding-top: 8px; margin-top: 8px; }
.tr[hidden] { display: none; }
.tools { display: flex; gap: 8px; margin-top: 10px; }
.chip { border: 1px solid var(--line); background: transparent; color: var(--ink); border-radius: 999px; padding: 6px 12px; font: inherit; font-size: 14px; cursor: pointer; }
.vf { display: flex; gap: 10px; }
.vf button { flex: 1; padding: 16px; font: inherit; font-size: 18px; font-weight: 700; border-radius: 12px; border: 2px solid var(--line);
  background: var(--card); color: var(--ink); cursor: pointer; }
.vf button.sel-ok { border-color: var(--ok); color: var(--ok); }
.vf button.sel-ko { border-color: var(--ko); color: var(--ko); }
.fb { font-weight: 700; margin: 10px 0; }
.fb.ok { color: var(--ok); } .fb.ko { color: var(--ko); }
.timer { font-variant-numeric: tabular-nums; font-weight: 700; }
.res { font-size: 28px; font-weight: 800; margin: 8px 0; }
.res.ok { color: var(--ok); } .res.ko { color: var(--ko); }
input[type=text] { width: 100%; padding: 12px; font: inherit; border-radius: 10px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }
.note { font-size: 13px; color: var(--grey); }
footer.legal { max-width: 680px; margin: 24px auto; padding: 0 16px 32px; font-size: 12px; color: var(--grey); }
/* 配图和「同一张图 第 k/n 题」标注；换成新图时边框闪一下，提醒用户图变了 */
figure.fig { margin: 0 0 12px; text-align: center; }
figure.fig img { margin-bottom: 6px; }
figure.fig figcaption { display: inline-block; font-size: 13px; color: var(--grey); border: 1px solid var(--line); border-radius: 999px; padding: 2px 10px; }
figure.fig.new img { animation: newfig 1.2s ease-out; }
@keyframes newfig { 0% { box-shadow: 0 0 0 4px var(--green-2); } 100% { box-shadow: 0 0 0 0 transparent; } }
.btn:disabled { opacity: .45; cursor: default; }
.rep { margin-top: 10px; display: grid; gap: 8px; }
.rep[hidden] { display: none; }
.rep .row { flex-wrap: wrap; gap: 6px 14px; }
.rep .opt { font-size: 14px; display: inline-flex; gap: 4px; align-items: center; }
.rep textarea { width: 100%; padding: 10px; font: inherit; border-radius: 10px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }
.rep .btn { margin: 0; text-align: center; }
p.foot { text-align: center; margin: 24px 0 8px; font-size: 13px; }
p.foot a { color: var(--grey); }
[dir="rtl"] .btn { text-align: right; }
[dir="rtl"] .btn.primary, [dir="rtl"] .row .btn { text-align: center; }
.nav { display: flex; gap: 8px; align-items: center; }
.nav [hidden] { display: none; }
.card.prog b { display: block; margin-bottom: 4px; }
.card.prog p { margin: 0 0 6px; }
.card.sale { text-align: center; }
.card.sale .price { font-size: 34px; font-weight: 800; color: var(--green-2); margin: 4px 0; }
.card.sale ul.feats { text-align: start; padding-inline-start: 20px; margin: 12px 0; }
.card.sale ul.feats li { margin: 6px 0; }
.card.rep input[type=text] { margin: 0; }
main a:not(.btn) { color: var(--green-2); }