/* ==========================================================================
   御藤国际 YT Schedule OS — Brand Theme V0.1
   Design tokens: see docs/YT_Schedule_OS_Design_System_V0.1.md
   规则：组件只引用 var(--yt-*)，不直接写色值；改主题只改 :root。
   ========================================================================== */

:root {
  /* --- Brand · 品牌色 --- */
  --yt-primary: #2B1B46;            /* Deep Purple 深紫：主按钮、侧栏、今日标记 */
  --yt-primary-hover: #3A2860;      /* 主按钮悬停 */
  --yt-primary-deep: #1F1433;       /* 侧栏底部、阴影色基 */
  --yt-primary-light: #564072;      /* Secondary Purple：次级文字、焦点环、班课标记 */
  --yt-primary-tint: #E6DFEF;       /* 紫色浅描边 */
  --yt-accent: #C9A96E;             /* Champagne Gold 香槟金：仅用于装饰、深色底上的强调 */
  --yt-accent-text: #8A6A2F;        /* 浅色底上的金色文字（满足 AA 4.5:1） */
  --yt-accent-soft: #F8F2E6;        /* 金色浅底：提示条、一对一卡片 */
  --yt-accent-line: #E8DCC2;        /* 金色浅描边 */

  /* --- Neutrals · 中性色 --- */
  --yt-background: #FAF9F7;         /* Warm White 页面底色 */
  --yt-surface: #FFFFFF;            /* 卡片 / 面板 */
  --yt-surface-secondary: #F1EDF5;  /* Light Lavender 区域底色 */
  --yt-surface-muted: #F7F5FA;      /* 表头、非本月日期、弱区域 */
  --yt-text-primary: #292535;       /* 正文 */
  --yt-text-secondary: #5E5870;     /* 次级文字 */
  --yt-text-tertiary: #6E6880;      /* 说明、小字（白底 5.3:1） */
  --yt-border: #E7E2EC;             /* 常规分隔线 */
  --yt-border-strong: #D5CDDF;      /* 输入框、按钮描边 */
  --yt-grid-line: #EFEBF3;          /* 日历小时线 */

  /* --- On dark (sidebar) · 深色底 --- */
  --yt-on-primary: #FFFFFF;
  --yt-on-primary-soft: #E9E4F0;
  --yt-on-primary-muted: #B3A8C6;
  --yt-on-primary-line: rgba(255, 255, 255, .12);
  --yt-on-primary-hover: rgba(255, 255, 255, .07);
  --yt-on-primary-active: rgba(255, 255, 255, .13);

  /* --- Status · 状态色（只表达状态，不作品牌色） --- */
  --yt-success: #2E7D32;
  --yt-success-bg: #EAF4EA;
  --yt-danger: #C62828;
  --yt-danger-text: #B42318;
  --yt-danger-bg: #FDF0EF;
  --yt-danger-line: #F1C9C4;
  --yt-warning: #E69A35;
  --yt-warning-text: #9A5B07;
  --yt-warning-bg: #FDF3E4;

  /* --- Calendar session cards · 课次卡片 --- */
  --yt-session-group-bg: #F1EDF5;
  --yt-session-group-bg-hover: #E7E0F0;
  --yt-session-group-line: #DCD2E8;
  --yt-session-group-mark: #564072;
  --yt-session-group-text: #2B1B46;
  --yt-session-group-meta: #564072;
  --yt-session-individual-bg: #F8F1E3;
  --yt-session-individual-bg-hover: #F2E7D0;
  --yt-session-individual-line: #E8DCC2;
  --yt-session-individual-mark: #B08D4F;
  --yt-session-individual-text: #4A3A20;
  --yt-session-individual-meta: #6B5427;
  --yt-session-cancelled-bg: #F4F3F6;
  --yt-session-cancelled-line: #D9D6DE;
  --yt-session-cancelled-text: #6E6880;

  /* --- Focus · 焦点 --- */
  --yt-focus: #564072;
  --yt-focus-on-dark: #C9A96E;

  /* --- Shape & elevation · 圆角与阴影 --- */
  --yt-radius-sm: 4px;
  --yt-radius-md: 8px;
  --yt-radius-lg: 12px;
  --yt-shadow-sm: 0 1px 2px rgba(31, 20, 51, .06);
  --yt-shadow-md: 0 1px 4px rgba(31, 20, 51, .10);
  --yt-shadow-lg: 0 24px 80px rgba(31, 20, 51, .22);
  --yt-backdrop: rgba(31, 20, 51, .45);

  /* --- Type · 字体 --- */
  --yt-font-serif: "Songti SC", "STSong", "Noto Serif SC", "Noto Serif CJK SC", "Source Han Serif SC", serif;
  --yt-font-sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", "Noto Sans CJK SC", system-ui, sans-serif;
}

/* ---------- Base ---------- */
* { box-sizing: border-box }
body { margin: 0; color: var(--yt-text-primary); background: var(--yt-background); font: 14px/1.6 var(--yt-font-sans) }
button, input, select, textarea { font: inherit }
button, a, input, select, textarea { -webkit-tap-highlight-color: transparent }
button { cursor: pointer; border: 1px solid var(--yt-border-strong); background: var(--yt-surface); color: var(--yt-text-primary); border-radius: var(--yt-radius-md); padding: 9px 15px; transition: background .15s, border-color .15s, color .15s }
button:hover { background: var(--yt-surface-secondary); border-color: var(--yt-primary-tint) }
button:active { background: var(--yt-primary-tint) }
button:disabled { opacity: .5; cursor: wait }
button:focus-visible, a:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible { outline: 3px solid var(--yt-focus); outline-offset: 2px }
a { color: inherit; text-decoration: none }

/* ---------- Sidebar ---------- */
.sidebar { width: 218px; position: fixed; inset: 0 auto 0 0; background: var(--yt-primary); background-image: linear-gradient(180deg, var(--yt-primary) 0%, var(--yt-primary) 70%, var(--yt-primary-deep) 100%); color: var(--yt-on-primary-soft); display: flex; flex-direction: column; padding: 32px 18px; z-index: 3 }
.sidebar :focus-visible { outline-color: var(--yt-focus-on-dark) }
.brand { display: flex; align-items: center; gap: 12px; padding: 0 8px; font: 22px var(--yt-font-serif); color: var(--yt-on-primary) }
.brand small { display: block; font: 9px var(--yt-font-sans); letter-spacing: 2px; margin-top: 8px; color: var(--yt-on-primary-muted) }
.brand-seal { border: 1px solid var(--yt-accent); border-radius: 2px; font-size: 27px; padding: 0 7px; color: var(--yt-accent) }
.workspace { font-size: 11px; color: var(--yt-on-primary-muted); display: flex; justify-content: space-between; padding: 34px 12px 16px }
.workspace span { color: var(--yt-accent); font-variant-numeric: tabular-nums }
.nav { position: relative; width: 100%; text-align: left; background: none; color: var(--yt-on-primary-soft); border: 0; display: flex; gap: 13px; align-items: center; margin: 3px 0; padding: 11px 14px }
.nav:hover { background: var(--yt-on-primary-hover); color: var(--yt-on-primary); border-color: transparent }
.nav.active { background: var(--yt-on-primary-active); color: var(--yt-on-primary) }
.nav.active::before { content: ""; position: absolute; left: 0; top: 10px; bottom: 10px; width: 3px; border-radius: 2px; background: var(--yt-accent) }
.nav-label { font-size: 10px; color: var(--yt-on-primary-muted); letter-spacing: 2px; padding: 22px 14px 8px }
.sidebar-foot { margin-top: auto; font-size: 11px; border-top: 1px solid var(--yt-on-primary-line); padding: 20px 12px 0 }
.sidebar-foot small { display: block; line-height: 1.9; color: var(--yt-on-primary-muted); margin-top: 10px }
.status-dot { display: inline-block; width: 6px; height: 6px; background: var(--yt-accent); border-radius: 100%; margin-right: 6px }

/* ---------- Main / header ---------- */
main { margin-left: 218px; padding: 0 38px 25px; max-width: 1800px }
.topbar { height: 70px; border-bottom: 1px solid var(--yt-border); display: flex; align-items: center; justify-content: space-between; font-size: 12px; color: var(--yt-text-tertiary) }
.topbar b { font-weight: 500; color: var(--yt-text-primary) }
.local-tag { border: 1px solid var(--yt-border-strong); border-radius: 5px; padding: 4px 10px; font-size: 10px; letter-spacing: 1px; color: var(--yt-text-secondary); background: var(--yt-surface) }
.intro { display: flex; justify-content: space-between; align-items: center; padding: 32px 0 23px; gap: 20px }
.eyebrow { font-size: 9px; letter-spacing: 2px; color: var(--yt-accent-text); font-weight: 600 }
h1 { font: 32px/1.4 var(--yt-font-serif); margin: 10px 0 8px; color: var(--yt-primary) }
p { margin: 0; color: var(--yt-text-tertiary); font-size: 12px }
.primary { background: var(--yt-primary); border-color: var(--yt-primary); color: var(--yt-on-primary); white-space: nowrap; padding: 11px 20px }
.primary:hover { background: var(--yt-primary-hover); border-color: var(--yt-primary-hover) }
.primary:active { background: var(--yt-primary-deep) }
.demo-banner { font-size: 11px; color: var(--yt-session-individual-meta); border: 1px solid var(--yt-accent-line); background: var(--yt-accent-soft); padding: 9px 14px; border-radius: 7px }
.demo-banner > span { font-weight: 600; letter-spacing: 1px; margin-right: 12px; color: var(--yt-accent-text) }

/* ---------- Stats ---------- */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin: 21px 0 }
.stat { position: relative; padding: 15px 19px; background: var(--yt-surface); border: 1px solid var(--yt-border); border-radius: 9px; box-shadow: var(--yt-shadow-sm) }
.stat span { font-size: 11px; color: var(--yt-text-tertiary) }
.stat strong { display: block; font-size: 27px; font-weight: 500; margin: 3px 0; color: var(--yt-primary); font-variant-numeric: tabular-nums }
.stat small { font-size: 10px; color: var(--yt-text-tertiary) }

/* ---------- Calendar shell ---------- */
.calendar-panel { background: var(--yt-surface); border: 1px solid var(--yt-border); border-radius: 10px; overflow: hidden; box-shadow: var(--yt-shadow-sm) }
.calendar-toolbar { display: flex; justify-content: space-between; align-items: center; padding: 19px 20px; gap: 10px }
.date-controls { display: flex; align-items: center; gap: 8px }
h2 { font-size: 17px; font-weight: 500; margin: 0 }
.date-controls h2 { margin: 0 9px; color: var(--yt-primary); font-variant-numeric: tabular-nums }
.icon { padding: 2px 10px; font-size: 22px; background: transparent; min-width: 31px; color: var(--yt-primary) }
.quiet { font-size: 11px; padding: 5px 11px }
.view-switch { background: var(--yt-surface-secondary); border: 1px solid var(--yt-border); padding: 3px; border-radius: 7px; display: flex }
.view-switch button { border: 0; background: none; font-size: 11px; padding: 5px 16px; color: var(--yt-text-secondary) }
.view-switch button:hover { background: var(--yt-surface); color: var(--yt-primary) }
.view-switch button.active { background: var(--yt-surface); box-shadow: var(--yt-shadow-md); color: var(--yt-primary); font-weight: 600 }
.filters { display: flex; gap: 15px; padding: 0 20px 16px; align-items: center; font-size: 11px; color: var(--yt-text-secondary) }
.filters label { display: flex; align-items: center; gap: 7px }
.filters select { padding: 5px 8px; width: 130px; font-size: 11px }
.check { white-space: nowrap }
.check input { accent-color: var(--yt-primary) }
.calendar-legend { margin-left: auto; color: var(--yt-text-tertiary); white-space: nowrap }
.calendar-legend i { display: inline-block; width: 7px; height: 7px; background: var(--yt-session-group-mark); margin: 0 5px 0 10px; border-radius: 2px }
.calendar-legend i.individual { background: var(--yt-session-individual-mark) }

/* ---------- Week / day view ---------- */
#calendar { overflow: auto; border-top: 1px solid var(--yt-border) }
.week-head { display: grid; grid-template-columns: 55px repeat(7, minmax(100px, 1fr)); min-width: 755px; position: sticky; top: 0; background: var(--yt-surface); z-index: 1 }
.week-head.day { grid-template-columns: 55px minmax(300px, 1fr); min-width: 0 }
.day-heading { padding: 11px; border-left: 1px solid var(--yt-border); text-align: center; font-size: 10px; color: var(--yt-text-tertiary) }
.day-heading strong { display: block; font-size: 19px; color: var(--yt-text-primary); font-weight: 500; font-variant-numeric: tabular-nums }
.day-heading.today { color: var(--yt-primary) }
.day-heading.today strong { background: var(--yt-primary); color: var(--yt-on-primary); border-radius: 50%; width: 30px; height: 30px; line-height: 30px; margin: 2px auto 0; font-size: 17px; box-shadow: 0 0 0 2px var(--yt-surface), 0 0 0 3px var(--yt-accent) }
.week-body { display: grid; grid-template-columns: 55px repeat(7, minmax(100px, 1fr)); min-width: 755px; height: 640px; overflow: auto }
.week-body.day { grid-template-columns: 55px minmax(300px, 1fr); min-width: 0 }
.hour-axis { position: relative; height: 1020px; color: var(--yt-text-tertiary); font-size: 9px; font-variant-numeric: tabular-nums }
.hour-axis span { position: absolute; right: 8px; transform: translateY(-50%) }
.day-column { position: relative; height: 1020px; border-left: 1px solid var(--yt-border); background: repeating-linear-gradient(to bottom, transparent 0, transparent 59px, var(--yt-grid-line) 59px, var(--yt-grid-line) 60px) }
.day-column.today { background-color: var(--yt-surface-muted) }

/* ---------- Session cards ---------- */
.event { position: absolute; left: 4px; right: 4px; border-radius: 5px; padding: 6px 7px; text-align: left; line-height: 1.35; font-size: 10px; overflow: hidden; background: var(--yt-session-group-bg); color: var(--yt-session-group-text); border: 1px solid var(--yt-session-group-line); border-left: 3px solid var(--yt-session-group-mark); min-height: 27px }
.event:hover { background: var(--yt-session-group-bg-hover); border-color: var(--yt-session-group-line); border-left-color: var(--yt-session-group-mark) }
.event.individual { background: var(--yt-session-individual-bg); color: var(--yt-session-individual-text); border-color: var(--yt-session-individual-line); border-left-color: var(--yt-session-individual-mark) }
.event.individual:hover { background: var(--yt-session-individual-bg-hover) }
.event.cancelled, .event.cancelled:hover { background: var(--yt-session-cancelled-bg); color: var(--yt-session-cancelled-text); border: 1px dashed var(--yt-session-cancelled-line); border-left: 3px solid var(--yt-session-cancelled-line); text-decoration: line-through }
.event b { display: block; font-weight: 600; font-size: 11px }
.event span { display: block; margin-top: 3px; color: var(--yt-session-group-meta) }
.event .event-time { font-size: 9px; margin: 0 0 4px; color: var(--yt-session-group-meta); font-variant-numeric: tabular-nums; font-weight: 600 }
.event.individual span, .event.individual .event-time { color: var(--yt-session-individual-meta) }
.event.cancelled span, .event.cancelled .event-time { color: var(--yt-session-cancelled-text) }
.calendar-footer { font-size: 10px; color: var(--yt-text-tertiary); border-top: 1px solid var(--yt-border); padding: 11px 18px; background: var(--yt-surface-muted) }

/* ---------- Month view ---------- */
.month-grid { display: grid; grid-template-columns: repeat(7, minmax(95px, 1fr)); min-width: 665px }
.month-heading { text-align: center; font-size: 10px; color: var(--yt-text-tertiary); padding: 10px; border-bottom: 1px solid var(--yt-border) }
.month-cell { min-height: 112px; padding: 7px; border-right: 1px solid var(--yt-border); border-bottom: 1px solid var(--yt-border); background: var(--yt-surface) }
.month-cell.other { background: var(--yt-surface-muted) }
.month-cell.other .month-day { color: var(--yt-text-tertiary) }
.month-day { padding: 0 5px; border: 0; background: none; font-size: 12px; font-variant-numeric: tabular-nums; border-radius: 6px }
.month-day:hover { background: var(--yt-surface-secondary); color: var(--yt-primary) }
.month-cell.today .month-day { background: var(--yt-primary); color: var(--yt-on-primary) }
.month-event { display: block; width: 100%; padding: 4px 6px; font-size: 10px; margin-top: 4px; border: 0; border-left: 2px solid var(--yt-session-group-mark); border-radius: 4px; background: var(--yt-session-group-bg); color: var(--yt-session-group-text); text-align: left; overflow: hidden; text-overflow: ellipsis; white-space: nowrap }
.month-event:hover { background: var(--yt-session-group-bg-hover); border-color: var(--yt-session-group-mark) }
.month-event.individual { background: var(--yt-session-individual-bg); color: var(--yt-session-individual-text); border-left-color: var(--yt-session-individual-mark) }
.month-event.individual:hover { background: var(--yt-session-individual-bg-hover) }
.month-event.cancelled { text-decoration: line-through; background: var(--yt-session-cancelled-bg); color: var(--yt-session-cancelled-text); border-left-color: var(--yt-session-cancelled-line) }
.empty { padding: 55px; text-align: center; color: var(--yt-text-tertiary) }

/* ---------- Tables (management pages) ---------- */
.table-wrap { margin-top: 22px; overflow: auto; background: var(--yt-surface); border: 1px solid var(--yt-border); border-radius: 9px; box-shadow: var(--yt-shadow-sm) }
table { border-collapse: collapse; width: 100%; font-size: 12px }
th { text-align: left; font-size: 10px; font-weight: 600; letter-spacing: .5px; color: var(--yt-text-secondary); background: var(--yt-surface-muted); white-space: nowrap }
td, th { padding: 14px 18px; border-bottom: 1px solid var(--yt-border) }
tbody tr:hover td { background: var(--yt-background) }
tbody tr:last-child td { border-bottom: 0 }
td b { color: var(--yt-primary); font-weight: 600 }
.table-actions { display: flex; gap: 6px }
.table-actions button { font-size: 10px; padding: 4px 8px }
.badge { display: inline-block; padding: 2px 7px; border-radius: var(--yt-radius-sm); background: var(--yt-success-bg); color: var(--yt-success); font-size: 10px; font-weight: 500 }
.badge.inactive { background: var(--yt-session-cancelled-bg); color: var(--yt-text-tertiary) }
.page-footer { font-size: 9px; color: var(--yt-text-tertiary); display: flex; justify-content: space-between; margin-top: 22px; letter-spacing: 1px }

/* ---------- Dialog & forms ---------- */
dialog { border: 0; padding: 0; border-radius: var(--yt-radius-lg); width: min(680px, 94vw); max-height: 90vh; box-shadow: var(--yt-shadow-lg); color: var(--yt-text-primary); background: var(--yt-surface) }
dialog::backdrop { background: var(--yt-backdrop); backdrop-filter: blur(3px) }
.modal-head { display: flex; justify-content: space-between; align-items: center; padding: 22px 25px; border-bottom: 1px solid var(--yt-border); border-top: 3px solid var(--yt-primary); border-radius: var(--yt-radius-lg) var(--yt-radius-lg) 0 0 }
.modal-head h2 { margin-top: 4px; color: var(--yt-primary) }
.modal-head .icon { border: 0 }
#modal-body { padding: 22px 25px }
form .form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 15px }
form label { display: block; font-size: 11px; color: var(--yt-text-secondary) }
input, select, textarea { display: block; width: 100%; border: 1px solid var(--yt-border-strong); border-radius: 6px; padding: 8px 10px; background: var(--yt-surface); color: var(--yt-text-primary); margin-top: 5px; min-width: 0; transition: border-color .15s, box-shadow .15s }
input:hover, select:hover, textarea:hover { border-color: var(--yt-primary-light) }
input:focus, select:focus, textarea:focus { border-color: var(--yt-primary-light) }
input:disabled, select:disabled, textarea:disabled { background: var(--yt-surface-muted); color: var(--yt-text-tertiary); cursor: not-allowed }
input:user-invalid, select:user-invalid, textarea:user-invalid { border-color: var(--yt-danger) }
input::placeholder, textarea::placeholder { color: var(--yt-text-tertiary); opacity: .8 }
textarea { resize: vertical; min-height: 70px }
.full { grid-column: 1/-1 }
.form-note { font-size: 10px; color: var(--yt-text-tertiary); margin: 5px 0 }
.form-actions { display: flex; justify-content: flex-end; gap: 8px; margin-top: 20px; padding-top: 17px; border-top: 1px solid var(--yt-border) }
.danger { border-color: var(--yt-danger-line); color: var(--yt-danger-text); background: var(--yt-surface) }
.danger:hover { background: var(--yt-danger-bg); border-color: var(--yt-danger) }
.error-box { padding: 12px; background: var(--yt-danger-bg); border: 1px solid var(--yt-danger-line); border-left: 3px solid var(--yt-danger); border-radius: 6px; color: var(--yt-danger-text); font-size: 12px; margin: 15px 0 }
.error-box ul { margin: 5px 0; padding-left: 20px }
.weekday-checks, .student-checks { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 8px }
.weekday-checks label, .student-checks label { display: flex; gap: 5px; align-items: center; padding: 5px 9px; border: 1px solid var(--yt-border-strong); border-radius: 5px; background: var(--yt-surface); color: var(--yt-text-primary) }
.weekday-checks label:has(input:checked), .student-checks label:has(input:checked) { border-color: var(--yt-primary-light); background: var(--yt-surface-secondary); color: var(--yt-primary) }
.weekday-checks input, .student-checks input { width: auto; margin: 0; accent-color: var(--yt-primary) }
.recurrence { border: 1px solid var(--yt-primary-tint); padding: 13px; border-radius: 7px; background: var(--yt-surface-secondary) }
.recurrence > .check { display: flex; align-items: center; gap: 7px; color: var(--yt-primary); font-weight: 500 }
.recurrence > .check input { width: auto; margin: 0 }
.detail-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 15px; margin: 16px 0 }
.detail-grid small { display: block; color: var(--yt-text-tertiary); font-size: 10px }
.detail-grid strong { font-weight: 500; font-size: 13px }
.detail-title { font: 24px var(--yt-font-serif); color: var(--yt-primary) }
.detail-note { white-space: pre-wrap; font-size: 12px; color: var(--yt-text-secondary); background: var(--yt-surface-secondary); padding: 12px; border-radius: 6px }

/* ---------- Toast ---------- */
#toast { position: fixed; bottom: 25px; left: 50%; transform: translate(-50%, 20px); opacity: 0; pointer-events: none; background: var(--yt-primary); color: var(--yt-on-primary); padding: 12px 23px; border-radius: var(--yt-radius-md); border-left: 3px solid var(--yt-accent); font-size: 12px; box-shadow: var(--yt-shadow-lg); transition: .2s; z-index: 9 }
#toast.show { opacity: 1; transform: translate(-50%, 0) }
[hidden] { display: none !important }

/* ---------- Responsive ---------- */
@media (max-width: 1050px) {
  main { padding: 0 22px 20px; margin-left: 185px }
  .sidebar { width: 185px; padding: 25px 12px }
  .brand { font-size: 19px }
  .filters { flex-wrap: wrap }
  .calendar-legend { margin-left: 0 }
}
@media (max-width: 740px) {
  .sidebar { position: static; width: 100%; padding: 14px }
  .brand { font-size: 18px }
  .brand small, .workspace, .sidebar-foot, .nav-label { display: none }
  .brand-seal { font-size: 21px }
  .sidebar nav { display: flex; overflow: auto; margin-top: 13px }
  .nav { width: auto; white-space: nowrap; padding: 8px }
  .nav > span { font-size: 11px }
  .nav { gap: 5px }
  .nav.active::before { left: 8px; right: 8px; top: auto; bottom: 0; width: auto; height: 2px }
  .nav-label { display: none }
  main { margin-left: 0; padding: 0 14px 18px }
  .topbar { height: 45px }
  .intro { padding: 24px 0 18px }
  h1 { font-size: 25px }
  .intro .primary { font-size: 11px; padding: 9px 11px }
  .stats { grid-template-columns: repeat(2, 1fr); gap: 9px }
  .stat { padding: 10px 13px }
  .calendar-toolbar { flex-wrap: wrap; padding: 12px }
  .date-controls h2 { font-size: 14px; margin: 0 2px }
  .filters { padding: 0 12px 12px; gap: 8px }
  form .form-grid { grid-template-columns: 1fr }
  .full { grid-column: auto }
  .demo-banner { font-size: 10px }
  .detail-grid { grid-template-columns: 1fr 1fr }
  #modal-body { padding: 18px }
  .modal-head { padding: 18px }
}
@media (prefers-reduced-motion: reduce) {
  * { transition: none !important }
}

/* All 24 hours remain accessible, including early lessons. */
.hour-axis, .day-column { height: 1440px }

/* ==========================================================================
   V0.2 · 登录、账号与协作（只引用 --yt-* 变量）
   ========================================================================== */
body.locked .sidebar, body.locked main { display: none }
body:not(.locked) .auth-screen { display: none }
.auth-screen { min-height: 100vh; display: grid; place-items: center; padding: 32px 16px; background: var(--yt-primary); background-image: radial-gradient(ellipse at 50% -10%, var(--yt-primary-light) 0%, var(--yt-primary) 55%, var(--yt-primary-deep) 100%) }
.auth-card { width: min(420px, 100%); background: var(--yt-surface); border-radius: var(--yt-radius-lg); padding: 34px 32px 26px; box-shadow: var(--yt-shadow-lg); border-top: 3px solid var(--yt-accent) }
.auth-card h1 { font-size: 24px; margin: 22px 0 4px }
.auth-sub { margin-bottom: 18px; line-height: 1.7 }
.auth-brand { display: flex; align-items: center; gap: 12px; font: 20px var(--yt-font-serif); color: var(--yt-primary) }
.auth-brand small { display: block; font: 9px var(--yt-font-sans); letter-spacing: 2px; margin-top: 4px; color: var(--yt-text-tertiary) }
.auth-brand .brand-seal { color: var(--yt-accent-text); border-color: var(--yt-accent); font-size: 24px }
.auth-card form > label { display: block; font-size: 11px; color: var(--yt-text-secondary); margin-bottom: 14px }
.auth-card input { padding: 10px 12px; font-size: 14px }
.auth-submit { width: 100%; margin-top: 6px; padding: 12px; font-size: 14px }
.auth-foot { margin-top: 18px; text-align: center; font-size: 10px; letter-spacing: 1px }
.auth-loading { text-align: center; color: var(--yt-text-tertiary); font-size: 12px; padding: 30px 0 }
.auth-card .form-actions { margin-top: 14px }
.user-card { display: flex; align-items: center; gap: 10px; margin-bottom: 10px }
.user-card b { display: block; color: var(--yt-on-primary); font-weight: 500; font-size: 13px }
.user-card small { display: block; color: var(--yt-on-primary-muted); font-size: 10px; margin: 0; line-height: 1.5 }
.user-avatar { width: 30px; height: 30px; flex: none; border-radius: 50%; display: grid; place-items: center; background: var(--yt-on-primary-active); color: var(--yt-accent); border: 1px solid var(--yt-accent); font: 14px var(--yt-font-serif) }
.user-actions { display: flex; gap: 14px; margin-bottom: 14px }
.link-button { background: none; border: 0; padding: 0; font-size: 11px; color: var(--yt-on-primary-soft); text-decoration: underline; text-decoration-color: var(--yt-on-primary-line); text-underline-offset: 3px }
.link-button:hover { background: none; color: var(--yt-accent); border: 0 }
.db-status { border-top: 1px solid var(--yt-on-primary-line); padding-top: 12px; color: var(--yt-on-primary-soft) }
.db-status small { display: block; line-height: 1.7; color: var(--yt-on-primary-muted); margin-top: 4px }
@media (max-width: 740px) {
  .sidebar-foot { display: block; border: 0; padding: 10px 0 0; margin-top: 8px }
  .user-card, .db-status { display: none }
  .user-actions { margin: 0; justify-content: flex-end }
}