/* 投屏端样式：大字号、高对比，适合教室投影 */
body.screen-body, body { background: linear-gradient(160deg, #eaf3fd 0%, #fdf6e9 100%); }

.screen-top { background: linear-gradient(90deg, #1f4e79, #2f7ce0); }
.clock { font-size: 15px; opacity: .9; font-variant-numeric: tabular-nums; }

.stage-tabs { display: flex; gap: 10px; justify-content: center; padding: 16px 12px 4px; flex-wrap: wrap; }
.stage-tabs button {
  border: 2px solid #c6d8ee; background: #fff; color: var(--blue-deep);
  font-size: 17px; font-weight: 700; padding: 10px 22px; border-radius: 999px; transition: all .15s;
}
.stage-tabs button:hover { border-color: var(--blue); }
.stage-tabs button.on { background: var(--blue); border-color: var(--blue); color: #fff; box-shadow: 0 4px 14px rgba(47,124,224,.35); }

.screen-main { max-width: 1200px; margin: 0 auto; padding: 18px 20px 40px; }
.stage { display: none; animation: fadeIn .35s ease; }
.stage.on { display: block; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }

.kicker { text-align: center; font-size: 22px; color: var(--muted); margin: 10px 0 18px; }

.mega-card {
  background: #fff; border-radius: 26px; padding: 40px 48px; display: flex; align-items: center; gap: 30px;
  box-shadow: 0 10px 30px rgba(31,78,121,.12); border: 3px solid #dbe9f8;
}
.mega-emoji { font-size: 90px; line-height: 1; }
.mega-text { font-size: 34px; line-height: 1.8; font-weight: 600; }
.wrong-card { border-color: #f3c3bb; background: #fff5f3; }
.wrong-card .mega-text b { color: var(--red); font-size: 40px; }

.ask-line { text-align: center; font-size: 26px; font-weight: 700; color: var(--blue-deep); margin: 26px 0 8px; }

.mega3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.m3 { background: #fff; border-radius: 22px; padding: 30px 18px; text-align: center; box-shadow: 0 8px 24px rgba(31,78,121,.10); border-top: 8px solid var(--blue); }
.m3 span { font-size: 34px; font-weight: 800; display: block; margin-bottom: 10px; }
.m3 small { font-size: 20px; color: var(--muted); line-height: 1.7; display: block; }
.m3.c1 { border-color: var(--orange); }
.m3.c2 { border-color: var(--green); }
.m3.c3 { border-color: var(--blue); }

.formula-mega {
  margin: 30px auto 10px; text-align: center; font-size: 52px; font-weight: 900; letter-spacing: 4px;
  color: #fff; background: linear-gradient(90deg, var(--orange), var(--blue)); border-radius: 22px;
  padding: 22px 30px; max-width: 760px; box-shadow: 0 10px 30px rgba(245,158,45,.35);
}

/* 问答流 */
.qa-feed { display: flex; flex-direction: column; gap: 14px; max-width: 900px; margin: 0 auto; }
.qa-pair { background: #fff; border-radius: 18px; padding: 16px 22px; box-shadow: 0 4px 16px rgba(31,78,121,.08); }
.qa-pair .who-line { font-size: 16px; color: var(--muted); margin-bottom: 6px; }
.qa-pair .q { font-size: 20px; line-height: 1.7; }
.qa-pair .a { font-size: 20px; line-height: 1.7; color: var(--blue-deep); font-weight: 600; margin-top: 6px; }
.qa-pair .a::before { content: '🧑‍🎓 答：'; color: var(--blue); }
.qa-empty { text-align: center; color: var(--muted); font-size: 22px; padding: 60px 0; }

/* 总结 */
.sum-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; max-width: 900px; margin: 26px auto; }
.sum-tile { background: #fff; border-radius: 16px; padding: 20px; text-align: center; box-shadow: 0 4px 14px rgba(31,78,121,.08); }
.sum-tile .n { font-size: 34px; font-weight: 800; color: var(--blue-deep); }
.sum-tile .l { color: var(--muted); font-size: 15px; margin-top: 4px; }
.sum-say { text-align: center; font-size: 22px; color: var(--ink); background: #e8f8f0; border-radius: 14px; padding: 16px 22px; max-width: 900px; margin: 8px auto; line-height: 1.8; }