/* 互动课（/learn/*）。色值与字体来自 /assets/brand/brand.css；版心比文章页宽，给视频留地方。
   荧绿只做点缀：按钮、选中态、标记，不当正文字色。交互在 learn.js。 */
.page-main.learn-main { width: min(1040px, 100% - 36px); padding-top: 48px; }
.learn [hidden] { display: none !important; }
.learn h1 { margin-bottom: 16px; }
.learn .lede { max-width: 30em; margin-bottom: 28px; }

/* 阶段标题（JS 生成，走正文字体，不依赖截字展示字体） */
.learn-h, .learn-q { font-family: var(--font-body); font-weight: 800; color: var(--text-hi); border: 0; padding: 0; outline: 0; }
.learn-h { font-size: clamp(24px, 3.4vw, 32px); line-height: 1.3; margin: 8px 0 20px; }
.learn-q { font-size: clamp(20px, 2.8vw, 26px); line-height: 1.6; margin: 22px 0 24px; max-width: 34em; }

/* 按钮 */
.learn-actions { display: flex; flex-wrap: wrap; gap: 12px; margin: 28px 0 0; }
.learn-btn {
  display: inline-flex; align-items: center; justify-content: center; min-height: 52px; padding: 12px 28px;
  border: 1px solid var(--lime); border-radius: 999px; background: var(--lime); color: #0d0d0d;
  font: 700 17px/1.3 var(--font-body); letter-spacing: .04em; cursor: pointer;
  transition: box-shadow .2s ease;
}
.learn-btn:hover { box-shadow: 0 0 0 5px rgba(198, 243, 107, .18); }
.learn-btn.is-ghost { background: transparent; color: var(--text-hi); border-color: var(--line-2); }
.learn-btn.is-ghost:hover { color: var(--lime); border-color: var(--lime); box-shadow: none; }
.learn-link { border: 0; background: none; padding: 8px 0; color: var(--text-mute); font: 15px/1 var(--font-body); cursor: pointer; text-decoration: underline; text-underline-offset: 4px; }
.learn-link:hover { color: var(--lime); }

/* 摸底进度 */
.learn-progress { display: flex; align-items: center; gap: 14px; }
.learn-count { font: 700 15px/1 var(--font-num); letter-spacing: .06em; color: var(--text-mute); white-space: nowrap; }
.learn-rail { flex: 1; height: 4px; border-radius: 2px; background: var(--line-2); overflow: hidden; }
.learn-rail i { display: block; height: 100%; background: var(--lime); transition: width .25s ease; }

/* 选项（摸底与提问点共用） */
.learn-options { display: grid; gap: 10px; max-width: 760px; }
.learn-opt {
  display: flex; align-items: flex-start; gap: 14px; width: 100%; min-height: 56px; padding: 14px 18px; text-align: left;
  border: 1px solid var(--line-2); border-radius: var(--radius-sm); background: var(--surface); color: var(--text-hi);
  font: 16.5px/1.6 var(--font-body); cursor: pointer; transition: border-color .15s ease, background-color .15s ease;
}
.learn-opt b { flex: none; width: 24px; font: 700 15px/1.7 var(--font-num); color: var(--lime); }
.learn-opt.is-unsure { color: var(--text-mute); padding-left: 56px; }
.learn-opt:hover { border-color: var(--text-mute); }
.learn-opt.is-picked { border-color: var(--lime); background: var(--surface-2); }
.learn-options.is-locked .learn-opt:not(.is-picked) { opacity: .5; }

/* 学习单 / 复习卡 */
.learn-cards { display: grid; gap: 14px; }
.learn-card { padding: 20px 22px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.learn-card.is-mastered { background: transparent; }
.learn-card-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: 6px 12px; }
.learn-card-title { flex: 1 1 16em; margin: 0; font-family: var(--font-body); font-size: 18px; line-height: 1.5; }
.learn-card-meta { font: 700 13px/1 var(--font-num); letter-spacing: .06em; color: var(--text-mute); }
.learn-tag { font: 700 13px/1 var(--font-body); letter-spacing: .08em; color: var(--text-mute); border: 1px solid var(--line-2); border-radius: 999px; padding: 5px 11px; }
.learn-tag.is-study { color: #0d0d0d; background: var(--lime); border-color: var(--lime); }
.learn-why { margin: 12px 0 0; font-size: 15.5px; line-height: 1.85; color: var(--text); }
.learn-review { margin: 12px 0 0; padding-left: 1.2em; font-size: 15.5px; line-height: 1.85; }
.learn-review li { margin: 3px 0; }

/* 播放 */
.learn-modbar { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.learn-stage { position: relative; margin-top: 4px; border: 1px solid var(--line-2); border-radius: 10px; overflow: hidden; background: #000; cursor: pointer; }
.learn-stage video { display: block; width: 100%; aspect-ratio: 16 / 9; background: #000; }
.learn-controls { display: flex; align-items: center; gap: 14px; margin-top: 12px; }
.learn-play { flex: none; min-width: 76px; min-height: 44px; padding: 0 16px; border: 1px solid var(--line-2); border-radius: 8px; background: var(--surface); color: var(--text-hi); font: 600 16px/1 var(--font-body); cursor: pointer; }
.learn-play:hover { border-color: var(--lime); }
.learn-seek { position: relative; flex: 1; height: 44px; cursor: pointer; touch-action: none; border-radius: 6px; }
.learn-seek-rail { position: absolute; left: 0; right: 0; top: 20px; height: 4px; border-radius: 2px; background: var(--line-2); }
.learn-seek-rail i { display: block; width: 0; height: 100%; border-radius: 2px; background: var(--lime); }
.learn-seek .mk { position: absolute; top: 12px; width: 4px; height: 20px; margin-left: -2px; border-radius: 2px; background: var(--text-hi); }
.learn-time { flex: none; min-width: 5.6em; text-align: right; font: 700 14px/1 var(--font-num); letter-spacing: .04em; color: var(--text-mute); }
.learn-chapters { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; }
.learn-chapter { min-height: 40px; padding: 0 14px; border: 1px solid var(--line-2); border-radius: 8px; background: transparent; color: var(--text); font: 15px/1 var(--font-body); cursor: pointer; }
.learn-chapter b { margin-right: 8px; color: var(--lime); font: 700 14px/1 var(--font-num); }
.learn-chapter:hover { border-color: var(--text-hi); color: var(--text-hi); }

/* 提问点：放在视频下面，手机竖屏也放得下 */
.learn-ask { margin-top: 18px; padding: 20px 22px 24px; border: 1px solid var(--lime); border-radius: var(--radius); background: var(--surface); }
.learn-ask-tag { margin: 0 0 8px; font: 700 14px/1 var(--font-num); letter-spacing: .08em; color: var(--lime); }
.learn-ask-q { margin: 0 0 16px; font: 700 clamp(18px, 2.4vw, 22px)/1.6 var(--font-body); color: var(--text-hi); }
.learn-ask .learn-options { margin-bottom: 20px; }

.learn-problem { margin: 18px 0 0; color: var(--text-hi); }
.learn-foot { margin: 56px 0 0; font-size: 13px; color: var(--text-mute); text-align: center; }

@media (max-width: 640px) {
  .page-main.learn-main { padding-top: 28px; }
  .learn-card { padding: 16px 16px; }
  .learn-btn { width: 100%; }
  .learn-controls { gap: 8px; }
  .learn-play { min-width: 64px; padding: 0 10px; }
  .learn-time { min-width: 5em; font-size: 13px; }
  .learn-ask { padding: 16px 16px 20px; }
}
@media (prefers-reduced-motion: reduce) {
  .learn-btn, .learn-opt, .learn-rail i { transition: none; }
}