/* 课堂：细头栏 + 舞台 + 悬浮控制条；写一写、问老师按需从右边展开，舞台让位 */

.lesson { position: absolute; inset: 0; display: flex; flex-direction: column; padding: 0 12px 12px; }
.lesson-head { min-height: 60px; flex: none; display: flex; align-items: center; gap: 8px; padding: 6px 0; min-width: 0; }
/* 课程名在上、当前环节在下，各占一整行；点开是环节目录 */
.lesson-title { display: flex; flex-direction: column; align-items: flex-start; justify-content: center; min-width: 0; flex: 0 1 auto; max-width: min(640px, 52vw); min-height: 48px; height: auto; padding: 2px 10px; margin-left: -2px; background: transparent; border-radius: 12px; text-align: left; color: var(--ink); }
.lesson-title > span { display: block; max-width: 100%; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.lesson-title .crumb { font: var(--t-caption); color: var(--muted-on-env); }
.lesson-title #stepTitle { font: var(--t-heading); }
.lesson-title[aria-expanded="true"] { background: var(--control); }
@media (hover: hover) and (pointer: fine) { .lesson-title:hover { background: var(--control-hover); } }
.lesson-title:active { scale: .985; }
.step-outline { position: absolute; z-index: 45; left: 56px; top: 60px; width: min(420px, calc(100% - 68px)); max-height: min(70vh, 560px); overflow-y: auto; overscroll-behavior: contain; padding: 14px 8px 8px; border-radius: var(--r-float); background: var(--float); box-shadow: var(--sh-float); transform-origin: 24px 0; animation: outline-in var(--d-state) var(--ease-out); }
@keyframes outline-in { from { opacity: 0; scale: .97; } }
.outline-course { margin: 0 12px 10px; font: var(--t-caption); color: var(--muted); }
.step-outline ol { list-style: none; margin: 0; padding: 0; }
.step-outline li button { display: grid; grid-template-columns: 28px 1fr; gap: 4px; align-items: baseline; width: 100%; min-height: 48px; height: auto; padding: 10px 12px; background: transparent; border-radius: 14px; text-align: left; font: var(--t-body); color: var(--ink-2); }
.step-outline li button .n { font: var(--t-caption); color: var(--faint); font-variant-numeric: tabular-nums; }
.step-outline li button[data-state="done"] { color: var(--muted); }
.step-outline li button[aria-current="step"] { background: var(--accent-tint); color: var(--accent-ink); font-weight: 600; }
.step-outline li button[aria-current="step"] .n { color: var(--accent); }
@media (hover: hover) and (pointer: fine) { .step-outline li button:not([aria-current]):hover { background: var(--control-hover); } }
.step-outline li button:active { scale: .985; }
.lesson-steps { display: flex; align-items: center; gap: 0; margin-left: 6px; flex: 0 1 auto; min-width: 0; max-width: 40vw; overflow-x: auto; scrollbar-width: none; }
.step-link { position: relative; min-height: 44px; height: 44px; min-width: 44px; width: 44px; padding: 0; background: transparent; border-radius: 12px; }
.step-link::before { content: ""; width: 14px; height: 4px; border-radius: 2px; background: var(--line-strong); transition: background var(--d-state), width 320ms var(--ease-out); }
.step-link[data-state="done"]::before { background: var(--ink-2); }
.step-link[aria-current="step"]::before { background: var(--accent); width: 22px; }
.step-link .number, .step-link .label { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.step-link .rail-tip { left: 50%; top: calc(100% + 2px); translate: -50% 0; }
.step-link[data-tip="show"] .rail-tip { opacity: 1; scale: 1; }
@media (hover: hover) and (pointer: fine) { .step-link:not(:disabled):hover { background: var(--control-hover); } }
.lesson-head .spacer { flex: 1; min-width: 8px; }
.save-cluster { display: inline-flex; align-items: center; gap: 6px; color: var(--muted-on-env); font: var(--t-caption); white-space: nowrap; min-width: 0; }
.save-cluster #saveStatus { overflow: hidden; text-overflow: ellipsis; max-width: 260px; }
.save-cluster #saveStatus.error { color: var(--danger); }
.save-dot { width: 7px; height: 7px; border-radius: 50%; background: var(--line-strong); flex: none; }
.save-dot[data-state="synced"] { background: var(--accent); }
.save-dot[data-state="conflict"], .save-dot[data-state="login"], .save-dot[data-state="rejected"], .save-dot[data-state="storage"] { background: var(--danger); }
.save-cluster .icon-btn { width: 44px; min-width: 44px; height: 44px; min-height: 44px; border-radius: 12px; }
.save-cluster .icon-btn .icon { width: 17px; height: 17px; }
.classroom-display-controls { display: inline-flex; align-items: center; gap: 4px; position: relative; }
.classroom-display-controls button { min-height: 44px; height: 44px; background: transparent; color: var(--ink-2); padding: 0 12px; }
.classroom-display-status { position: absolute; right: 0; top: calc(100% + 6px); z-index: 40; width: max-content; max-width: 320px; margin: 0; padding: 8px 12px; border-radius: 12px; background: var(--float); box-shadow: var(--sh-float); font: var(--t-caption); color: var(--ink-2); }
:root[data-classroom-display="focus"] .lesson { position: fixed; z-index: 50; background: var(--env); }

.lesson-notice {
  position: absolute; z-index: 30; left: 50%; top: 64px; translate: -50% 0; max-width: min(560px, calc(100% - 32px)); margin: 0;
  padding: 8px 14px; border-radius: 12px; background: var(--float); box-shadow: var(--sh-float); font: var(--t-caption); color: var(--ink-2);
  opacity: 0; pointer-events: none; transition: opacity var(--d-state) var(--ease-out);
}
.lesson-notice[data-show="true"] { opacity: 1; }
.lesson > .inline-error { margin: 0 0 10px; }

.lesson-body { flex: 1; min-height: 0; display: flex; gap: 12px; position: relative; padding-right: var(--help-space, 0px); }
.stage { container-type: inline-size; position: relative; flex: 1; min-width: 0; background: var(--paper); border-radius: var(--r-paper); box-shadow: var(--sh-paper); overflow: hidden; }
.stage-scroll { position: absolute; inset: 0; overflow-y: auto; overscroll-behavior: contain; padding: 28px clamp(20px, 4cqw, 48px) 112px; display: flex; flex-direction: column; }

/* ---------- 舞台上的讲解 ---------- */
.teaching-board { width: 100%; max-width: 860px; margin: 0 auto; flex: 1 0 auto; display: flex; flex-direction: column; }
.guided-ribbon { display: flex; align-items: center; gap: 12px; color: var(--muted); font: var(--t-caption); margin-bottom: 8px; }
.guided-phase { color: var(--ink-2); }
.teaching-board[data-mode="answer"] .guided-phase, .teaching-board[data-mode="feedback"] .guided-phase { color: var(--accent-ink); }
.guided-stage { flex: 1 0 auto; display: flex; flex-direction: column; justify-content: center; gap: 18px; padding: 18px 0 8px; min-height: min(52vh, 420px); }
.teaching-board[data-mode="answer"] .guided-stage, .teaching-board[data-mode="feedback"] .guided-stage, .teaching-board[data-mode="complete"] .guided-stage { min-height: 0; flex: 0 0 auto; }
.guided-headline { font: 600 calc(clamp(22px, 2.4vw, 28px) * (.5 + var(--board-scale, 1) / 2))/1.4 var(--font); margin: 0; letter-spacing: -.005em; }
.lesson-figure { min-width: 0; }
.generic-board { font: 400 calc(clamp(20px, 2.3vw, 28px) * var(--board-scale, 1))/1.7 var(--font); color: var(--ink); white-space: pre-line; overflow-x: auto; overflow-y: hidden; }
.generic-board .katex { font-size: 1.08em; }
/* 板书逐行出现：没讲到的行先占位不显示，讲到时淡入 */
.board-line { transition: opacity 420ms var(--ease-out), translate 420ms var(--ease-out); }
.board-line.line-hidden { opacity: 0; translate: 0 6px; }
/* 开场路线：这节课要回答的几个问题，编号 + 一句话，跟着讲解一站站出现 */
.board-route { list-style: none; margin: 4px 0 0; padding: 0; display: flex; flex-direction: column; gap: 14px; white-space: normal; }
.board-route .board-line { display: grid; grid-template-columns: 40px 1fr; align-items: baseline; gap: 12px; }
.board-route .route-n { width: 32px; height: 32px; border-radius: 50%; display: grid; place-items: center; align-self: center; background: var(--control); color: var(--ink-2); font: 600 15px/1 var(--font); font-variant-numeric: tabular-nums; }
.question-hint { font: var(--t-body); color: var(--ink-2); }
.question-hint summary { display: inline-flex; align-items: center; min-height: 44px; padding: 0 14px; border-radius: var(--r-control); background: var(--control); color: var(--ink-2); font: var(--t-control); cursor: pointer; list-style: none; }
.question-hint summary::-webkit-details-marker { display: none; }
.question-hint[open] summary { background: var(--accent-tint); color: var(--accent-ink); }
.question-hint p { margin: 10px 0 0; }
/* 字缩到下限还放不下时，宽屏的纯板书分两栏 */
.teaching-board[data-fit="columns"] .generic-board { column-count: 2; column-gap: 40px; }
.teaching-board[data-fit="columns"] .generic-board .board-line { break-inside: avoid; }
.guided-caption { margin: 0; font: var(--t-caption); color: var(--muted); }
.screen-note { margin: 0; font: var(--t-body); color: var(--ink-2); }
.teaching-board[data-playing="true"] .guided-headline { color: var(--ink); }
.stage .reveal { animation: none; }

/* 旧示范课的学科图示（线上已下架，保持可读） */
.lesson-figure[role="img"], .method-chain, .independent-task, .energy-chart { display: flex; flex-wrap: wrap; gap: 14px; align-items: stretch; }
.system-zone, .transfer-zone, .environment-zone, .method-chain > div, .independent-task, .energy-chart { flex: 1 1 160px; padding: 14px 16px; border-radius: 16px; box-shadow: inset 0 0 0 1px var(--line); display: flex; flex-direction: column; gap: 4px; }
.zone-eyebrow, .zone-detail, .method-chain small, .method-chain span { font: var(--t-caption); color: var(--muted); }
.beaker { width: 64px; height: 64px; fill: none; stroke: var(--ink-2); stroke-width: 2; }
.beaker .liquid { fill: var(--accent-tint); stroke: none; }
.transfer-line { height: 2px; background: var(--accent); margin: 8px 0; }
.reasoning-slots { display: flex; gap: 8px; flex-wrap: wrap; font: var(--t-caption); }
.reasoning-slots span { padding: 4px 10px; border-radius: 10px; background: var(--control); }
.task-number { font: 600 28px/1.2 var(--font); }
.energy-chart .level, .energy-chart .enthalpy-drop, .energy-chart .energy-equation, .energy-chart .energy-axis { font: var(--t-control); }
.cross-diagram { margin-top: 8px; padding: 16px 18px; border-radius: 16px; box-shadow: inset 0 0 0 1px var(--line); font: var(--t-body); }
.cross-diagram p { margin: 0 0 8px; }
.cross-controls { display: flex; gap: 8px; flex-wrap: wrap; margin: 6px 0 10px; }
.cross-controls button[aria-pressed="true"] { background: var(--ink); color: #fff; }
.cross-diagram table { border-collapse: collapse; margin: 10px 0; font: var(--t-control); }
.cross-diagram th, .cross-diagram td { padding: 6px 12px; border-bottom: 1px solid var(--line); text-align: left; }

/* 普通课的板书（非引导课） */
.teaching-board[data-kind="board"] { justify-content: center; }
.question-row { width: 100%; max-width: 860px; margin: 18px auto 0; display: flex; align-items: flex-start; gap: 12px; padding: 14px 16px; border-radius: 16px; background: var(--accent-tint); }
.question-row h2 { font: var(--t-caption); color: var(--accent-ink); margin: 0 0 4px; }
.question-row p { margin: 0; font: var(--t-body); }
.question-row > div { flex: 1; }
.question-mark { display: none; }
.source-details { width: 100%; max-width: 860px; margin: 22px auto 0; color: var(--muted); font: var(--t-caption); }
.source-details summary { min-height: 36px; display: inline-flex; align-items: center; }
.source-details p { margin: 4px 0; }
.source-details a { display: block; color: var(--accent-ink); }

/* ---------- 题目、作答与讲评（都在舞台上） ---------- */
.answer-shortcut { align-self: flex-start; margin-top: 8px; background: transparent; color: var(--ink-2); box-shadow: inset 0 0 0 1px var(--line); }
.guided-question, .guided-feedback, .guided-summary { margin-top: 18px; display: flex; flex-direction: column; gap: 12px; }
.guided-question h3, .guided-feedback h3, .guided-summary h3, .reasoning-review h3 { font: var(--t-caption); color: var(--muted); margin: 0; font-weight: 400; }
.question-context { font: 400 20px/1.7 var(--font); margin: 0; }
.guided-question form { display: flex; flex-direction: column; gap: 12px; }
.guided-question fieldset { border: 0; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 10px; }
.answer-option {
  min-height: 54px; border-radius: 16px; display: flex; align-items: center; gap: 12px; padding: 10px 16px; cursor: pointer;
  box-shadow: inset 0 0 0 1px var(--line); font: var(--t-body); transition: box-shadow var(--d-state), background var(--d-state), transform var(--d-press) var(--ease-out);
}
.answer-option:active { transform: scale(.985); }
.answer-option:has(input:checked) { box-shadow: inset 0 0 0 1.5px var(--accent); background: var(--accent-tint); }
.answer-option:has(input:focus-visible) { outline: 2px solid var(--accent); outline-offset: 3px; }
.answer-option input { flex: none; }
.answer-error { margin: 0; color: var(--danger); font: var(--t-control); min-height: 0; }
.answer-error:empty { display: none; }
#submitJudgment { align-self: flex-start; background: var(--ink); color: #fff; font-weight: 600; }
#submitJudgment:disabled { background: var(--control-press); color: var(--muted); font-weight: 400; }
.feedback-scope { margin: 0; font: var(--t-caption); color: var(--muted); }
.lesson-write { align-self: flex-start; }
.guided-feedback { padding-top: 4px; }
.feedback-label { align-self: flex-start; padding: 4px 10px; border-radius: 10px; font: var(--t-caption); background: var(--control); color: var(--ink-2); }
.chosen-answer { margin: 0; font: var(--t-body); }
.feedback-explanation { margin: 0; font: var(--t-reading); font-size: 18px; }
.reasoning-review { padding: 16px 18px; border-radius: 16px; box-shadow: inset 0 0 0 1px var(--line); display: flex; flex-direction: column; gap: 8px; }
.reasoning-review strong { font: var(--t-heading); }
.reasoning-review[data-verdict="correct"] strong { color: var(--accent-ink); }
.reasoning-review p { margin: 0; }
.reasoning-evidence { display: grid; gap: 4px; }
.reasoning-evidence blockquote { margin: 0; padding-left: 12px; border-left: 3px solid var(--accent-soft); color: var(--ink); }
.reasoning-next { color: var(--accent-ink); }
.feedback-retry { align-self: flex-start; }
.guided-feedback > .feedback-retry, #retryJudgment { margin-top: 2px; }
.submission-original { display: grid; grid-template-columns: minmax(0, 1fr); gap: 8px; }
.submission-original img { width: 100%; max-width: 420px; border-radius: 14px; background: #fdfdfb; box-shadow: inset 0 0 0 1px var(--line); }
.submission-original p { margin: 0; font: var(--t-body); color: var(--ink-2); white-space: pre-wrap; }
.versions { display: inline-flex; gap: 4px; flex-wrap: wrap; }
.versions button { min-height: 34px; height: 34px; padding: 0 10px; border-radius: 9px; font: var(--t-caption); }
.versions button[aria-pressed="true"] { background: var(--ink); color: #fff; }
.guided-summary { padding: 22px 0 0; }
.guided-summary h3 { font: var(--t-title); color: var(--ink); }
.guided-summary p { margin: 0; color: var(--ink-2); }
.summary-download { align-self: flex-start; }
.guided-summary[data-kind="next"] h3 { font: var(--t-caption); color: var(--muted); }
.guided-summary .summary-next { font: var(--t-title); color: var(--ink); }
.summary-goals { margin: 0; padding-left: 1.2em; color: var(--ink-2); font: var(--t-body); }
.submission-records { margin-top: 18px; display: flex; flex-direction: column; gap: 8px; color: var(--muted); font: var(--t-caption); }
.submission-records:empty { display: none; }
.submission-records > p:empty { display: none; }
.submission-records > p { margin: 0; }
.submission-records > button { align-self: flex-start; }
.submission-records details summary { min-height: 36px; display: inline-flex; align-items: center; color: var(--ink-2); }
.submission-record { padding: 10px 0; border-top: 1px solid var(--line); }
.submission-record p { margin: 0 0 4px; }

/* ---------- 悬浮控制条 ---------- */
.controls {
  position: absolute; z-index: 6; left: 50%; bottom: 18px; translate: -50% 0; max-width: calc(100% - 24px);
  display: flex; align-items: center; gap: 2px; padding: 6px; border-radius: 22px; background: var(--float); box-shadow: var(--sh-float);
}
.controls .sep { width: 1px; height: 24px; background: var(--line); margin: 0 6px; flex: none; }
.ctl { min-height: 48px; height: 48px; min-width: 48px; padding: 0 12px; border-radius: 16px; background: transparent; flex: none; }
.ctl[aria-pressed="true"], .ctl[aria-expanded="true"] { background: var(--control); }
.ctl:disabled { opacity: .38; background: transparent; }
.ctl.play, .lesson-play { width: 52px; min-width: 52px; padding: 0; background: var(--ink); color: #fff; font-size: 0; }
.ctl.play:active, .lesson-play:active { background: #33353b; }
.lesson-play .icon { width: 20px; height: 20px; }
.lesson-play .i-pause { display: none; }
.lesson-play[aria-pressed="true"] .i-play { display: none; }
.lesson-play[aria-pressed="true"] .i-pause { display: block; }
/* 慢网卡住时：按钮图标呼吸，文字显示“缓冲中” */
.lesson-play[aria-busy="true"] .icon { animation: lesson-buffering 1.1s ease-in-out infinite alternate; }
@keyframes lesson-buffering { from { opacity: 1; } to { opacity: .35; } }
@media (prefers-reduced-motion: reduce) { .lesson-play[aria-busy="true"] .icon { animation: none; opacity: .5; } }
:root[data-motion="reduced"] .lesson-play[aria-busy="true"] .icon { animation: none; opacity: .5; }
.ctl.ask { padding: 0 14px 0 10px; transition: padding var(--d-space) var(--ease-space), background var(--d-state); }
.lesson-player, .lesson-player-host { display: contents; }
.lesson-player progress { display: none; }
.lesson-time { flex: none; font: var(--t-caption); color: var(--muted); max-width: 160px; padding: 0 8px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.lesson-replay { min-height: 48px; height: 48px; padding: 0 12px; border-radius: 16px; background: transparent; }
/* 控制条变窄时文字收成纯图标：宽度和透明度一起过渡，不是一下子消失 */
.ctl { gap: 0; }
.ctl-label { display: inline-block; max-width: 5em; margin-left: 8px; overflow: hidden; white-space: nowrap; vertical-align: middle;
  transition: max-width var(--d-space) var(--ease-space), margin-left var(--d-space) var(--ease-space), opacity 200ms var(--ease-out); }
@media (hover: hover) and (pointer: fine) {
  .ctl:not(:disabled):hover, .lesson-replay:not(:disabled):hover { background: var(--control); }
  .ctl.play:not(:disabled):hover, .lesson-play:not(:disabled):hover { background: #33353b; }
}
@container (max-width: 760px) { .controls .ctl-label { max-width: 0; margin-left: 0; opacity: 0; } .controls .ctl.ask { padding: 0 12px; } .lesson-time { display: none; } }
@container (max-width: 520px) { .controls .sep { margin: 0 2px; } }
/* 手机宽：收起“重听”和分隔线，五个主操作都放得下 */
@container (max-width: 420px) { .controls .sep, .controls .lesson-replay { display: none; } .controls { gap: 0; padding: 4px; } .ctl { min-width: 44px; padding: 0 10px; } .ctl.play, .lesson-play { width: 48px; min-width: 48px; } .ctl.ask { padding: 0 10px; } }

/* 讲稿：默认收起，只显示当前这一段 */
.script {
  position: absolute; z-index: 5; left: 50%; bottom: 88px; translate: -50% 0; width: min(640px, calc(100% - 32px)); max-height: 46%;
  overflow-y: auto; background: var(--float); border-radius: 18px; box-shadow: var(--sh-float); padding: 14px 18px; font: var(--t-body); color: var(--ink-2);
}
.script p { margin: 0 0 6px; }
.script .narration-text { color: var(--ink); }
.voice-settings { margin-top: 8px; font: var(--t-caption); color: var(--muted); }
.voice-settings summary { min-height: 36px; display: inline-flex; align-items: center; }
.rate-label { display: flex; align-items: center; gap: 10px; }
.rate-label input { flex: 1; }
.rate-note { margin: 4px 0 0; }

/* ---------- 写一写：从右边展开，舞台让位 ---------- */
.dock { position: relative; flex: none; width: 0; overflow: hidden; border-radius: var(--r-paper); transition: width var(--d-space) var(--ease-space); }
.lesson[data-write="open"] .dock { width: min(44vw, 520px); }
.lesson[data-write="open"][data-help="open"] .dock { width: min(34vw, 440px); }
.lesson[data-write="focus"] .dock { width: min(68vw, 900px); }
.dock-paper { position: absolute; top: 0; bottom: 0; left: 0; width: min(44vw, 520px); background: var(--paper); border-radius: var(--r-paper); box-shadow: var(--sh-paper); display: flex; flex-direction: column; overflow: hidden; }
.lesson[data-write="open"][data-help="open"] .dock-paper { width: min(34vw, 440px); }
.lesson[data-write="focus"] .dock-paper { width: min(68vw, 900px); }
.dock-head { min-height: 58px; flex: none; display: flex; align-items: center; gap: 8px; padding: 6px 8px 0 18px; }
.dock-head h2 { font: var(--t-heading); margin: 0; }
.dock-mode { padding: 3px 9px; border-radius: 9px; font: var(--t-caption); background: var(--control); color: var(--ink-2); }
.dock[data-mode="answer"] .dock-mode { background: var(--accent-tint); color: var(--accent-ink); }
.dock-head .spacer { flex: 1; }
.note-prompt { margin: 2px 18px 8px; padding: 8px 12px; border-radius: 12px; background: var(--accent-tint); color: var(--accent-ink); font: var(--t-control); }
.note-prompt:empty { display: none; }
.ink-toolbar { display: flex; align-items: center; gap: 2px; padding: 0 12px 8px; flex-wrap: wrap; }
.ink-toolbar .tool-group { display: inline-flex; gap: 2px; }
.ink-toolbar button { min-height: 44px; height: 44px; min-width: 44px; padding: 0 10px; background: transparent; color: var(--ink-2); border-radius: 12px; }
.ink-toolbar button[aria-pressed="true"] { background: var(--control); color: var(--ink); }
.ink-toolbar button .icon { width: 19px; height: 19px; }
.toolbar-separator { width: 1px; height: 22px; background: var(--line); margin: 0 6px; }
.width-label { display: inline-flex; align-items: center; gap: 6px; margin-left: auto; font: var(--t-caption); color: var(--muted); }
.width-label select { min-height: 44px; padding: 6px 10px; font: var(--t-control); }
.paper-scroll { position: relative; flex: 1; min-height: 120px; margin: 0 12px; overflow: auto; border-radius: 16px; box-shadow: inset 0 0 0 1px var(--line); background-color: #fcfcfd; background-image: radial-gradient(circle, #d9dbe1 1px, transparent 1.2px); background-size: 22px 22px; }
.dock[data-mode="answer"] .paper-scroll { background: #fff repeating-linear-gradient(to bottom, transparent 0 43px, #e9ebef 43px 44px); }
/* 笔迹全部交给页面处理（手指滑动由 InkBoard 自己滚动）；交给浏览器会把笔的上下移动当成滚动而断笔 */
#ink { display: block; width: 100%; aspect-ratio: 10 / 9; touch-action: none; }
.paper-empty { position: absolute; left: 0; right: 0; top: 34%; display: grid; justify-items: center; gap: 4px; color: var(--muted); font: var(--t-control); pointer-events: none; }
.paper-empty .icon { color: var(--faint); }
.paper-empty small { font: var(--t-caption); }
.text-note-label { margin: 10px 18px 4px; font: var(--t-caption); color: var(--muted); }
#textNote { margin: 0 12px; min-height: 52px; max-height: 120px; font-size: 15px; resize: none; }
.dock-foot { flex: none; display: flex; align-items: center; gap: 8px; padding: 8px 12px 12px; color: var(--muted); font: var(--t-caption); flex-wrap: wrap; }
.dock-foot .spacer { flex: 1; }
.dock-foot button.primary { min-height: 44px; }
.dock .conflict { margin: 0 12px 8px; }

/* ---------- 问老师：右侧边栏（竖屏和窄屏改为底部面板） ---------- */
.classroom-help-backdrop { position: fixed; inset: 0; z-index: 59; background: rgba(27, 28, 32, .18); opacity: 0; pointer-events: none; }
.lesson-help-dialog {
  display: block; position: fixed; z-index: 60; right: 0; margin: 0; border: 0; padding: 60px 12px 12px 0; width: 384px; max-width: 100vw;
  height: var(--visible-height, 100dvh); background: transparent; color: var(--ink); will-change: transform;
}
.lesson-help-dialog .tdock-paper { height: 100%; background: var(--paper); border-radius: var(--r-paper); box-shadow: var(--sh-paper); display: flex; flex-direction: column; overflow: hidden; }
.lesson-help-dialog[data-layout="sheet"] { left: 0; width: 100%; padding: 0; height: min(78dvh, var(--visible-height, 100dvh)); }
.lesson-help-dialog[data-layout="sheet"] .tdock-paper { border-radius: var(--r-paper) var(--r-paper) 0 0; box-shadow: var(--sh-float); }
.tdock-head { min-height: 58px; flex: none; display: flex; align-items: center; gap: 10px; padding: 6px 8px 0 16px; }
.tdock-head h2 { font: var(--t-heading); margin: 0; flex: 1; }
.tdock-body { flex: 1; min-height: 0; overflow-y: auto; overscroll-behavior: contain; padding: 4px 16px 16px; display: flex; flex-direction: column; gap: 12px; }
.help-position { margin: 0; padding: 8px 12px; border-radius: 12px; background: var(--env); color: var(--ink-2); font: var(--t-caption); }
.help-common-title { font: var(--t-caption); color: var(--muted); margin: 8px 0 0; font-weight: 400; }
.tdock-body > details { font: var(--t-control); }
.tdock-body > details summary { min-height: 40px; display: flex; align-items: center; }
.tdock-body > details p { margin: 0 0 8px; color: var(--ink-2); }
#resumeLesson { align-self: stretch; margin-top: 4px; }

.teacher-help { display: flex; flex-direction: column; gap: 12px; }
.teacher-connection { display: flex; align-items: center; justify-content: space-between; gap: 8px; color: var(--muted); font: var(--t-caption); }
.teacher-connection .help-retry { min-height: 36px; height: 36px; font: var(--t-caption); background: transparent; color: var(--ink-2); }
.teacher-check-result { margin: 0; font: var(--t-caption); color: var(--muted); }
.teacher-check-result:empty { display: none; }
.teacher-check-result[data-result="error"] { color: var(--danger); }
.teacher-check-result[data-result="success"] { color: var(--accent-ink); }
.help-status { margin: 0; font: var(--t-caption); color: var(--muted); }
.help-records { display: flex; flex-direction: column; gap: 14px; }
.help-records:empty { display: none; }
.help-record { display: flex; flex-direction: column; gap: 8px; }
.help-record > summary { list-style: none; align-self: flex-end; max-width: 88%; padding: 10px 14px; border-radius: 16px 16px 4px 16px; background: var(--control); font: var(--t-body); white-space: pre-wrap; }
.help-record > summary::-webkit-details-marker { display: none; }
.help-answer { font: var(--t-body); color: var(--ink); margin-top: 8px; overflow-x: auto; }
.help-answer p { margin: 0 0 8px; }
.help-work { font: var(--t-caption); color: var(--muted); }
.help-work summary { min-height: 32px; display: inline-flex; align-items: center; }
.help-ink-preview { max-width: 100%; border-radius: 12px; background: #fff; box-shadow: inset 0 0 0 1px var(--line); }
.help-retry { align-self: flex-start; min-height: 38px; height: 38px; font: var(--t-caption); }
.reply-voice { display: flex; flex-direction: column; gap: 6px; }
.reply-voice .help-privacy { margin: 0; }
.help-privacy { margin: 0; font: var(--t-caption); color: var(--muted); }
.help-pending { display: flex; flex-direction: column; gap: 8px; font: var(--t-caption); color: var(--ink-2); }
.help-pending:empty { display: none; }
.help-pending p { margin: 0; }

.teacher-help-form { display: flex; flex-direction: column; gap: 8px; }
.help-question-label { font: var(--t-caption); color: var(--muted); }
.help-composer {
  position: relative; display: flex; align-items: flex-end; gap: 4px; padding: 6px 6px 6px 12px; border-radius: 20px; background: var(--paper);
  box-shadow: var(--sh-touch), 0 0 0 1px var(--line); transition: box-shadow var(--d-state) var(--ease-out);
}
.help-composer:focus-within { box-shadow: var(--sh-touch), 0 0 0 1px var(--line-strong), 0 0 0 4px var(--accent-soft); }
.help-composer .help-question { flex: 1; min-width: 0; min-height: 44px; max-height: 128px; border: 0; box-shadow: none; padding: 10px 2px; background: transparent; resize: none; font: var(--t-body); line-height: 1.5; transition: opacity var(--d-fade); }
.help-composer .help-question:focus { box-shadow: none; }
.help-composer .help-question:focus-visible, .composer textarea:focus-visible { outline: none; }
.help-composer .voice-input { flex: none; display: block; }
.help-composer[data-action="send"] .voice-input { display: none; }
.voice-record { width: 44px; min-width: 44px; height: 44px; min-height: 44px; padding: 0; border-radius: 50%; background: transparent; color: var(--ink-2); }
.voice-record[aria-pressed="true"] { background: var(--ink); color: #fff; border-radius: 14px; }
.voice-record:disabled { background: transparent; color: var(--faint); }
.voice-record-glyph { display: block; width: 24px; height: 24px; margin: auto; overflow: visible; }
.voice-bars { position: absolute; left: 16px; right: 60px; top: 50%; height: 28px; margin-top: -14px; display: flex; align-items: center; justify-content: space-between; gap: 2px; pointer-events: none; opacity: 0; clip-path: inset(0 0 0 100%); }
.voice-bars i { display: block; flex: none; width: 2px; height: 26px; border-radius: 3px; background: var(--ink-2); transform: scaleY(.09); transition: transform 45ms linear; }
.teacher-help-form[data-voice-mode="recording"] .help-composer .help-question, .teacher-help-form[data-voice-mode="permission"] .help-composer .help-question { opacity: 0; pointer-events: none; }
.teacher-help-form[data-voice-mode="permission"] .voice-bars { opacity: .6; }
#askTeacher { width: 44px; min-width: 44px; height: 44px; min-height: 44px; padding: 0; border-radius: 50%; font-size: 0; background: var(--ink); color: #fff; }
#askTeacher::before { content: ""; width: 22px; height: 22px; background: currentColor; -webkit-mask: var(--send-mask) center / contain no-repeat; mask: var(--send-mask) center / contain no-repeat; }
.lesson-help-dialog { --send-mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='1.9' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M12 19V5.5M6.5 11 12 5.5l5.5 5.5'/%3E%3C/svg%3E"); }
#askTeacher:disabled { background: var(--control); color: var(--faint); }
.help-voice-recovery { display: flex; flex-wrap: wrap; align-items: center; gap: 6px 10px; }
.help-voice-recovery .voice-input-status { flex-basis: 100%; margin: 0; font: var(--t-caption); color: var(--muted); }
.help-voice-recovery .voice-input-status[hidden] { display: none; }
.help-voice-recovery .help-question { flex-basis: 100%; min-height: 82px; }
.teacher-help-form[data-voice-mode="recording"] .help-voice-recovery .voice-input-status { position: absolute; width: 1px; height: 1px; margin: -1px; overflow: hidden; clip: rect(0 0 0 0); }
.teacher-help-form[data-voice-mode="recording"] .help-voice-recovery .help-privacy, .teacher-help-form[data-voice-mode="permission"] .help-voice-recovery .help-privacy { display: none; }
.help-include-notes {
  align-self: flex-start; display: inline-flex; align-items: center; gap: 8px; min-height: 36px; padding: 0 12px 0 10px; border-radius: 11px;
  background: var(--control); font: var(--t-caption); color: var(--ink-2); cursor: pointer;
}
.help-include-notes:has(input:checked) { background: var(--accent-tint); color: var(--accent-ink); box-shadow: inset 0 0 0 1px var(--accent-ring); }
.help-attachment { display: flex; gap: 8px; align-items: flex-start; }
.help-attachment .help-ink-preview { width: 120px; }
.help-note-text { margin: 0; font: var(--t-caption); color: var(--ink-2); white-space: pre-wrap; max-height: 80px; overflow: hidden; }
.help-new-question { align-self: flex-start; min-height: 36px; font: var(--t-caption); background: transparent; color: var(--ink-2); }

/* ---------- 竖屏与窄屏 ---------- */
@media (max-width: 900px), (orientation: portrait) {
  .lesson-body { flex-direction: column; padding-right: 0; }
  .lesson-steps { display: none; }
  .lesson-title { max-width: none; flex: 1 1 auto; }
  .dock { width: auto !important; height: 0; transition: height var(--d-space) var(--ease-space); }
  .lesson[data-write="open"] .dock, .lesson[data-write="focus"] .dock { height: 52%; }
  .lesson[data-write="focus"] .dock { height: 78%; }
  .dock-paper, .lesson[data-write] .dock-paper { width: 100% !important; }
  #ink { aspect-ratio: 10 / 9; }
}
@media (max-width: 560px) {
  .lesson { padding: 0 8px 8px; }
  .save-cluster #saveStatus { display: none; }
  .controls { bottom: 12px; }
  .stage-scroll { padding: 20px 18px 110px; }
  .classroom-display-controls button { padding: 0 8px; }
}

/* ---------- 课堂图示（lesson-figure/1）：左图右板书，讲到哪指到哪 ---------- */
.guided-stage.has-figure { position: relative; }
.figure-layout { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: clamp(16px, 3cqw, 32px); align-items: center; }
.figure-layout.board-only { grid-template-columns: minmax(0, 1fr); }
.figure-main { display: grid; gap: 8px; justify-items: center; }
.figure-wrap { display: grid; gap: 6px; justify-items: center; width: 100%; }
.figure-svg { width: 100%; height: auto; max-height: calc(100vh - 300px); overflow: visible; }
.figure-caption { margin: 0; font: var(--t-caption); color: var(--muted); text-align: center; }
.figure-board { display: flex; flex-direction: column; gap: 8px; min-width: 0; padding-left: 22px; }
.figure-board .board-line { font: 400 calc(clamp(19px, 2.1vw, 25px) * var(--board-scale, 1))/1.6 var(--font); color: var(--ink); overflow-x: hidden; overflow-y: hidden; border-radius: 8px; padding: 0 4px; margin: 0 -4px; transition: color 600ms var(--ease-out), background-color 600ms var(--ease-out), opacity 420ms var(--ease-out), translate 420ms var(--ease-out); }
.figure-board .board-line.figure-lit { background: var(--accent-tint); }

.figure-svg .lbl { font: 600 17px var(--font); fill: var(--ink); transition: fill 600ms var(--ease-out); }
.figure-svg .lbl.sub { font-weight: 400; font-size: 15px; fill: var(--ink-2); }
.figure-svg .lbl.sign { font-weight: 600; font-size: 17px; }
.figure-svg .power-box { fill: var(--paper); stroke: var(--ink-2); stroke-width: 2; }
.figure-svg .power-mark { stroke: var(--ink-2); stroke-width: 2; stroke-linecap: round; fill: none; }
.figure-svg .wire, .figure-svg .vessel { fill: none; stroke: var(--ink-2); stroke-width: 2; stroke-linejoin: round; stroke-linecap: round; }
.figure-svg .liquid { fill: var(--solution); }
.figure-svg .liquid-line { stroke: var(--solution-line); stroke-width: 1.5; }
.figure-svg .molten .liquid { fill: var(--molten); }
.figure-svg .molten .liquid-line { stroke: var(--line-strong); }
.figure-svg .membrane-line { stroke: var(--ink-2); stroke-width: 2; stroke-dasharray: 6 5; }
.figure-svg .electrode-body { fill: var(--graphite); }
.figure-svg .deposit { fill: var(--deposit); }
.figure-svg .deposit.copper { fill: var(--copper); }
.figure-svg .erode { fill: var(--solution); }
.figure-svg .erode.molten { fill: var(--molten); }
.figure-svg .electrode-ghost { fill: none; stroke: var(--graphite); stroke-width: 1.2; stroke-dasharray: 4 3; }
.figure-svg .bubble { fill: var(--paper); stroke: var(--ink-2); stroke-width: 1.3; }
.figure-svg .product-label { font-size: 15px; }
.figure-svg .ion-ring { fill: var(--paper); stroke-width: 1.6; }
.figure-svg .ion-ring.cation { stroke: var(--copper); }
.figure-svg .ion-ring.anion { stroke: var(--graphite); stroke-width: 1.4; }
.figure-svg .ion-label { font: 600 12px var(--font); fill: var(--ink); }
.figure-svg .flow { fill: none; stroke: var(--accent); stroke-width: 2.2; stroke-linecap: round; }
.figure-svg .flow-head { fill: var(--accent); }
.figure-svg .flow-label { fill: var(--accent-ink); }
/* 讲到时被指的部分短暂变成强调色 */
.figure-svg .figure-lit .lbl, .figure-svg .lbl.figure-lit, .figure-svg .figure-lit .ion-label { fill: var(--accent); }
.figure-svg .figure-lit .ion-ring { stroke: var(--accent); }
.figure-svg .electrode.figure-lit .electrode-body { fill: color-mix(in srgb, var(--graphite) 70%, var(--accent)); }
.figure-svg [data-element] { transition: opacity 420ms var(--ease-out); }
.figure-svg .figure-hidden { opacity: 0; }
@keyframes figure-enter { from { opacity: 0; } to { opacity: 1; } }

/* 指点：出现、移动、停住。不扩散、不循环 */
.figure-pointer { position: absolute; left: 0; top: 0; width: 14px; height: 14px; margin: -7px 0 0 -7px; z-index: 3; pointer-events: none; border-radius: 50%; background: var(--accent); box-shadow: 0 0 0 5px var(--accent-soft); opacity: 0; transition: transform 600ms cubic-bezier(.34, 1.12, .64, 1), opacity 320ms var(--ease-out); }
.figure-pointer[data-visible="true"] { opacity: 1; }
.figure-pointer[data-instant="true"] { transition: opacity 320ms var(--ease-out); }

/* 课件原图 */
.source-page { display: grid; gap: 6px; width: 100%; }
.source-page-view { position: relative; overflow: hidden; width: 100%; border-radius: 12px; background: var(--control); box-shadow: inset 0 0 0 1px var(--line); max-height: calc(100vh - 300px); }
.source-page-canvas { position: absolute; }
.source-page-canvas img { display: block; width: 100%; height: 100%; object-fit: fill; user-select: none; }
.source-page[data-state="loading"] .source-page-canvas img, .source-page[data-state="failed"] .source-page-canvas { opacity: 0; }
.source-page[data-state="ready"] .source-page-canvas img { animation: figure-enter 320ms var(--ease-out); }
.source-mark { position: absolute; border-radius: 6px; transition: box-shadow 600ms var(--ease-out), background-color 600ms var(--ease-out); }
.source-mark.figure-lit { box-shadow: 0 0 0 2px var(--accent); background: var(--accent-soft); }
.source-page-status { margin: 0; display: flex; align-items: center; gap: 10px; font: var(--t-caption); color: var(--muted); }
.source-page .figure-caption { text-align: left; }

/* 出处 */
.figure-refs { display: flex; flex-wrap: wrap; gap: 6px 14px; }
.figure-ref { font: var(--t-caption); color: var(--muted); background: none; border: 0; padding: 6px 0; min-height: 32px; text-decoration: underline; text-decoration-color: var(--line-strong); text-underline-offset: 3px; cursor: pointer; }
.figure-ref:active { transform: scale(.975); }
.figure-ref:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
@media (hover: hover) and (pointer: fine) { .figure-ref:hover { color: var(--ink-2); text-decoration-color: currentColor; } }
.source-viewer { border: 0; padding: 0; border-radius: var(--r-float); box-shadow: var(--sh-float); background: var(--float); width: min(920px, calc(100vw - 32px)); max-height: calc(100vh - 32px); color: var(--ink); }
.source-viewer::backdrop { background: rgba(20, 22, 28, .28); }
.source-viewer-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 12px 12px 8px 20px; }
.source-viewer-head h2 { margin: 0; font: var(--t-heading); }
.source-viewer-body { padding: 0 20px 20px; display: grid; gap: 8px; }
.source-viewer-body img { display: block; width: 100%; height: auto; max-height: calc(100vh - 120px); object-fit: contain; border-radius: 10px; box-shadow: inset 0 0 0 1px var(--line); }
.source-viewer[data-state="loading"] .source-viewer-body img { min-height: 240px; background: var(--control); color: transparent; }
.source-viewer[data-state="failed"] .source-viewer-body img { display: none; }

/* 竖屏或很窄时上图下板书，图尽量大 */
@media (orientation: portrait) { .figure-layout { grid-template-columns: minmax(0, 1fr); } .figure-svg { max-height: 48vh; } }
@container (max-width: 640px) { .figure-layout { grid-template-columns: minmax(0, 1fr); } .figure-svg { max-height: 46vh; } }
@media (prefers-reduced-motion: reduce) {
  .figure-pointer, .figure-svg [data-element], .figure-board .board-line, .source-mark { transition: none; }
  .source-page[data-state="ready"] .source-page-canvas img { animation: none; }
}
:root[data-motion="reduced"] .figure-pointer, :root[data-motion="reduced"] .figure-svg [data-element] { transition: none; }