:root { color-scheme: light; --ink: #172c35; --muted: #52646d; --line: #d7e0e3; --brand: #126565; --brand-soft: #e9f5f2; --danger: #b42331; --danger-soft: #fff0f1; --background: #f7f8fa; }
* { box-sizing: border-box; }
[hidden] { display: none !important; }
body { margin: 0; background: var(--background); color: var(--ink); font: 16px/1.6 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif; }
button, select { font: inherit; }
button, a, select { -webkit-tap-highlight-color: transparent; touch-action: manipulation; }
button, select { min-height: 44px; }
button { cursor: pointer; }
button:disabled, select:disabled { cursor: not-allowed; }
button:focus-visible, select:focus-visible, a:focus-visible { outline: 3px solid #377dcc; outline-offset: 3px; }
a { color: var(--brand); text-underline-offset: 3px; }
h1, h2, h3, p { margin-top: 0; }
h1 { font-size: 26px; line-height: 1.4; margin-bottom: 0; }
h2 { font-size: 18px; margin-bottom: 0; }
h3 { font-size: 16px; margin-bottom: 8px; }
.classroom-shell { max-width: 780px; margin: 0 auto; padding: max(24px, env(safe-area-inset-top)) max(18px, env(safe-area-inset-right)) max(28px, env(safe-area-inset-bottom)) max(18px, env(safe-area-inset-left)); }
.page-header { display: flex; justify-content: space-between; align-items: center; gap: 16px; margin-bottom: 24px; }
.brand { color: var(--brand); font-size: 13px; font-weight: 650; margin-bottom: 4px; letter-spacing: .08em; }
.text-link { display: inline-flex; align-items: center; min-height: 44px; white-space: nowrap; font-size: 14px; }
.notice { padding: 12px 14px; margin-bottom: 16px; background: #edf2f6; border: 1px solid #d7e1e8; border-radius: 10px; font-size: 14px; overflow-wrap: anywhere; }
.notice-error { background: #fff5e6; color: #713d05; border-color: #edd4ad; }
.class-picker { display: grid; gap: 7px; margin-bottom: 22px; }
.class-picker label { color: var(--muted); font-size: 14px; }
select { width: 100%; border-radius: 12px; border: 1px solid #acbdc3; padding: 12px; color: var(--ink); background: #fff; font-weight: 650; }
.section-heading { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 10px; }
.muted { color: var(--muted); font-size: 14px; }
.instructions { font-size: 14px; color: var(--muted); margin-bottom: 20px; }
.recording-banner { position: sticky; top: max(8px, env(safe-area-inset-top)); z-index: 3; background: var(--danger); color: #fff; border-radius: 12px; padding: 14px 16px; margin: 0 0 16px; box-shadow: 0 4px 18px #b4233124; display: flex; align-items: center; gap: 9px; flex-wrap: wrap; }
.recording-banner p { width: 100%; font-size: 13px; margin: 0; }
#recording-clock { margin-left: auto; font-size: 23px; font-variant-numeric: tabular-nums; font-weight: 700; line-height: 1.2; }
.record-dot { display: inline-block; width: 9px; height: 9px; background: currentColor; border-radius: 50%; flex-shrink: 0; }
.student-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 8px; }
.student-card { display: flex; flex-direction: column; min-width: 0; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; background: #fff; transition: border-color 150ms; }
.student-record { flex: 1; width: 100%; min-height: 76px; padding: 10px 4px; display: flex; flex-direction: column; justify-content: center; align-items: center; gap: 4px; border: 0; background: #fff; color: var(--ink); }
.student-name { max-width: 100%; font-weight: 750; font-size: 16px; overflow-wrap: anywhere; line-height: 1.4; }
.student-count { max-width: 100%; font-size: 12px; line-height: 1.45; color: var(--muted); }
.student-action { display: none; max-width: 100%; font-size: 12px; line-height: 1.45; overflow-wrap: anywhere; color: var(--brand); font-weight: 650; }
.student-details { width: 100%; min-height: 44px; padding: 6px 4px; border: 0; border-top: 1px solid var(--line); background: #fbfcfc; color: var(--brand); font-size: 12px; line-height: 1.4; }
.student-card.is-recording { border: 2px solid var(--danger); }
.student-card.is-recording .student-record { background: var(--danger-soft); color: var(--danger); }
.student-card.is-recording .student-action { display: block; color: var(--danger); font-weight: 750; }
.student-card.is-locked .student-record { background: #f0f2f3; color: #718087; }
.student-card.is-locked .student-action { color: #617078; }
.student-card.is-locked .student-count { color: #617078; }
.student-record:active { background: var(--brand-soft); }
.student-card.is-recording .student-record:active { background: #ffe0e3; }
.records-section, .pending-section { margin-top: 30px; padding-top: 22px; border-top: 1px solid var(--line); }
.secondary-button { border: 1px solid #b6c7cd; color: var(--brand); border-radius: 9px; background: #fff; padding: 7px 12px; font-size: 14px; flex-shrink: 0; }
.secondary-button:disabled { opacity: .55; }
.record-list { display: grid; gap: 12px; }
.record-item { background: #fff; border: 1px solid var(--line); padding: 16px; border-radius: 12px; min-width: 0; }
.record-meta { display: flex; gap: 8px; align-items: baseline; justify-content: space-between; flex-wrap: wrap; margin-bottom: 9px; }
.record-status { display: inline-block; color: var(--brand); font-size: 13px; font-weight: 650; }
.record-transcript { white-space: pre-wrap; overflow-wrap: anywhere; font-size: 16px; margin: 10px 0; }
.record-warning { color: #8a4708; font-size: 13px; margin: 8px 0; }
.record-item audio { width: 100%; min-height: 44px; margin-top: 6px; }
.record-actions { display: flex; gap: 12px; flex-wrap: wrap; align-items: center; margin-top: 10px; }
.record-actions a { display: inline-flex; min-height: 44px; align-items: center; font-size: 14px; }
.empty-state { padding: 25px 16px; color: var(--muted); text-align: center; background: #fff; border-radius: 12px; border: 1px dashed var(--line); }
.page-footnote { color: var(--muted); font-size: 12px; margin-top: 30px; margin-bottom: 0; }
@media (min-width: 520px) { .student-grid { grid-template-columns: repeat(5, minmax(0, 1fr)); } }
@media (min-width: 680px) { .student-grid { grid-template-columns: repeat(6, minmax(0, 1fr)); } .classroom-shell { padding-top: 36px; } }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { transition: none !important; scroll-behavior: auto !important; } }