:root {
  color-scheme: light;
  --background: #f1f5f9;
  --surface: #ffffff;
  --surface-soft: #f8fafc;
  --text: #0f172a;
  --text-secondary: #475569;
  --border: #cbd5e1;
  --accent: #0f766e;
  --accent-hover: #115e59;
  --accent-soft: #ccfbf1;
  --error: #9f1239;
  --error-surface: #fff1f2;
  --radius-control: 8px;
  --radius-section: 12px;
  --radius-workspace: 16px;
  --font: "Noto Sans JP", "Yu Gothic", "Hiragino Sans", sans-serif;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { background: var(--background); }
body { margin: 0; color: var(--text); font: 16px/1.6 var(--font); }
h1, h2, p { margin: 0; }
h1 { font-size: 24px; font-weight: 700; line-height: 1.35; }
h2 { font-size: 18px; font-weight: 700; line-height: 1.5; }
button, select { font: inherit; }
button, select, summary { min-height: 44px; }
button {
  padding: 9px 15px;
  border: 1px solid var(--border);
  border-radius: var(--radius-control);
  background: var(--surface);
  color: var(--text);
  font-weight: 600;
  cursor: pointer;
  transition: background-color 120ms ease, border-color 120ms ease;
}
button:hover:enabled { background: var(--surface-soft); border-color: var(--text-secondary); }
button:disabled { cursor: not-allowed; color: var(--text-secondary); background: var(--surface-soft); }
.primary-button { background: var(--accent); color: white; border-color: var(--accent); }
.primary-button:hover:enabled { background: var(--accent-hover); border-color: var(--accent-hover); }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }
::selection { color: var(--text); background: var(--accent-soft); }
.skip-link { position: absolute; top: -80px; left: 16px; padding: 12px; background: var(--surface); color: var(--accent); z-index: 2; }
.skip-link:focus { top: 12px; }
.app-header { background: var(--surface); border-bottom: 1px solid var(--border); }
.header-inner { max-width: 1440px; margin: 0 auto; padding: 24px 32px; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.app-title p { color: var(--text-secondary); margin-top: 4px; font-size: 14px; }
.session-controls { display: flex; gap: 8px; flex-shrink: 0; }
.workspace { max-width: 1440px; margin: 0 auto; padding: 20px 32px 32px; }
.session-status { margin-bottom: 20px; }
#status { font-weight: 600; }
.workspace-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(300px, 340px); align-items: start; border: 1px solid var(--border); border-radius: var(--radius-workspace); overflow: hidden; background: var(--surface); }
.lecture-column, .help-column { min-width: 0; }
.help-column { border-left: 1px solid var(--border); }
.caption-panel { padding: 24px; }
.section-heading { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 8px; margin-bottom: 16px; min-height: 44px; }
.caption-scroll { overflow-y: auto; overflow-x: hidden; scrollbar-gutter: stable; overscroll-behavior: contain; overflow-anchor: none; padding: 12px 16px; border: 1px solid var(--border); border-radius: var(--radius-section); background: var(--surface); }
.caption-scroll p { white-space: pre-wrap; overflow-wrap: anywhere; }
.translation-scroll { height: clamp(240px, 36vh, 390px); }
#translated-caption { font-size: clamp(24px, 2.2vw, 30px); line-height: 1.9; font-weight: 500; line-break: strict; }
.transcript-panel { border-top: 1px solid var(--border); background: var(--surface-soft); }
.transcript-scroll { height: clamp(200px, 28vh, 310px); }
#source-caption { font-size: 19px; line-height: 1.85; }
.selection-hint { margin-top: 16px; font-size: 14px; color: var(--text-secondary); }
.jump-button { padding: 7px 12px; font-size: 14px; color: var(--accent); }
.help-settings, .help-section { padding: 24px; }
.help-settings { background: var(--surface-soft); }
.help-settings label { display: block; font-weight: 600; margin-bottom: 8px; }
select { width: 100%; padding: 8px 36px 8px 12px; border: 1px solid var(--border); border-radius: var(--radius-control); background: var(--surface); color: var(--text); }
.help-settings p, .supporting-text { font-size: 14px; color: var(--text-secondary); line-height: 1.65; }
.help-settings p { margin-top: 8px; }
.help-section { border-top: 1px solid var(--border); }
.help-section h2 { margin-bottom: 16px; }
.field-label { color: var(--text-secondary); font-size: 14px; margin-bottom: 4px; }
.selected-phrase { font-size: 18px; font-weight: 600; overflow-wrap: anywhere; margin-bottom: 16px; }
#explain-button { width: 100%; }
.supporting-text:not(:empty), .error-message:not(:empty) { margin-top: 12px; }
.error-message:not(:empty) { padding: 12px; border-left: 3px solid var(--error); border-radius: 0 var(--radius-control) var(--radius-control) 0; background: var(--error-surface); color: var(--error); overflow-wrap: anywhere; font-size: 14px; }
.phrase-translation:not(:empty) { font-size: 22px; font-weight: 700; margin-top: 20px; overflow-wrap: anywhere; }
.explanation-text:not(:empty) { margin-top: 12px; line-height: 1.9; overflow-wrap: anywhere; }
audio { display: block; width: 100%; margin-top: 16px; }
.help-list { list-style: none; padding: 0; margin: 0; }
.saved-help { margin-top: 20px; padding-top: 16px; border-top: 1px solid var(--border); overflow-wrap: anywhere; }
.saved-help .match-kind { color: var(--text-secondary); font-size: 13px; margin-bottom: 4px; }
.saved-help strong { display: block; font-size: 17px; }
.help-translation { font-size: 20px; line-height: 1.8; margin: 8px 0; }
summary { padding: 10px 0; cursor: pointer; font-weight: 600; font-size: 14px; }
details > p { margin: 8px 0; }
details > button { margin: 8px 8px 0 0; }
.remove-button { color: var(--error); border: 0; padding-left: 0; text-decoration: underline; text-underline-offset: 3px; font-size: 14px; margin-top: 8px; }
mark { color: inherit; background: transparent; }
mark button { min-height: 0; display: inline; padding: 0 2px; border: 0; border-radius: 2px; font: inherit; color: var(--accent-hover); background: var(--accent-soft); text-decoration: underline; text-underline-offset: 4px; }
mark button:hover:enabled { background: var(--accent-soft); color: var(--text); }

@media (max-width: 1000px) {
  .header-inner { padding: 20px 24px; }
  .workspace { padding: 16px 24px 24px; }
  .workspace-grid { grid-template-columns: minmax(0, 1fr) minmax(270px, 300px); }
  .caption-panel, .help-settings, .help-section { padding: 20px; }
}
@media (max-width: 760px) {
  .header-inner { padding: 20px 16px; align-items: flex-start; flex-direction: column; gap: 16px; }
  .workspace { padding: 16px; }
  .workspace-grid { grid-template-columns: minmax(0, 1fr); }
  .help-column { border-left: 0; border-top: 1px solid var(--border); }
  .help-settings { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 8px 16px; align-items: center; }
  .help-settings label { margin: 0; }
  .help-settings p { grid-column: 1 / -1; margin: 0; }
  .caption-panel, .help-settings, .help-section { padding: 20px 16px; }
  .translation-scroll { height: 260px; }
  .transcript-scroll { height: 220px; }
  #source-caption { font-size: 18px; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; scroll-behavior: auto !important; }
}