:root {
  color-scheme: light;
  --blue: #174ea6;
  --blue-dark: #0c326f;
  --blue-soft: #eaf3ff;
  --ink: #14263d;
  --muted: #5e7087;
  --line: #d9e4f0;
  --panel: #ffffff;
  --page: #f4f7fb;
  --green: #137a4f;
  --green-soft: #e8f7ef;
  --amber: #976100;
  --amber-soft: #fff4d8;
  --red: #a52a2a;
  --shadow: 0 16px 42px rgba(24, 67, 111, .10);
}

* { box-sizing: border-box; }
html { min-width: 320px; background: var(--page); }
body { margin: 0; color: var(--ink); background: var(--page); font: 16px/1.55 system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif; }
button, input, select, textarea { font: inherit; }
button, select { cursor: pointer; }
.hidden { display: none !important; }
.skip-link { position: fixed; left: 12px; top: -60px; z-index: 20; padding: 10px 14px; color: #fff; background: var(--blue-dark); border-radius: 8px; }
.skip-link:focus { top: 12px; }

.topbar { min-height: 68px; padding: 10px clamp(18px, 4vw, 54px); display: flex; align-items: center; justify-content: space-between; gap: 18px; color: #fff; background: linear-gradient(110deg, var(--blue-dark), var(--blue)); }
.brand { display: inline-flex; align-items: center; gap: 10px; color: inherit; text-decoration: none; font-weight: 850; letter-spacing: .01em; }
.brand-mark { width: 38px; height: 38px; display: grid; place-items: center; border-radius: 11px; color: var(--blue); background: #fff; font-size: 23px; }
.account-area { display: flex; align-items: center; gap: 12px; font-weight: 700; }

main { width: min(1180px, calc(100% - 32px)); margin: 0 auto; }
.login-view { min-height: calc(100vh - 68px); display: grid; place-items: center; padding: 36px 0; }
.login-card { width: min(470px, 100%); display: grid; gap: 10px; padding: clamp(24px, 5vw, 42px); border: 1px solid var(--line); border-radius: 22px; background: var(--panel); box-shadow: var(--shadow); }
.login-card h1 { margin: 0; font-size: clamp(30px, 6vw, 44px); }
.login-copy { margin: 0 0 16px; color: var(--muted); }
.login-card label { margin-top: 5px; font-weight: 750; }
.login-card input, .class-picker select { width: 100%; min-height: 48px; padding: 10px 13px; border: 1px solid #aec0d4; border-radius: 10px; color: var(--ink); background: #fff; }
.login-card input:focus, .class-picker select:focus, button:focus-visible { outline: 3px solid #7db3ff; outline-offset: 2px; }
.form-error { min-height: 24px; margin: 2px 0; color: var(--red); font-weight: 700; }
.privacy-note { margin: 6px 0 0; color: var(--muted); font-size: 13px; }

.button { min-height: 42px; padding: 9px 16px; border: 1px solid transparent; border-radius: 10px; font-weight: 800; }
.button.large { min-height: 50px; }
.button.primary { color: #fff; background: var(--blue); }
.button.secondary { color: var(--blue); background: #fff; border-color: #9eb7d5; }
.button.ghost { color: #fff; background: transparent; border-color: rgba(255,255,255,.5); }
.button:disabled { cursor: wait; opacity: .65; }

.dashboard { padding: 42px 0 70px; }
.page-heading, .section-heading { display: flex; align-items: end; justify-content: space-between; gap: 24px; }
.page-heading h1 { margin: 2px 0 4px; font-size: clamp(30px, 5vw, 48px); line-height: 1.1; }
.page-heading p { margin: 0; color: var(--muted); }
.eyebrow, .section-kicker { margin: 0; color: var(--blue); font-size: 12px; font-weight: 900; letter-spacing: .13em; }
.picker-group { width: min(390px, 100%); display: grid; gap: 12px; }
.class-picker { width: 100%; display: grid; gap: 6px; font-weight: 800; }

.summary-grid { margin: 30px 0; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 14px; }
.summary-card { padding: 20px; border: 1px solid var(--line); border-radius: 16px; background: var(--panel); box-shadow: 0 8px 24px rgba(24,67,111,.06); }
.summary-card strong { display: block; font-size: 30px; line-height: 1.15; }
.summary-card span { color: var(--muted); font-size: 14px; }

.student-section, .manage-section { padding: clamp(20px, 4vw, 32px); border: 1px solid var(--line); border-radius: 20px; background: var(--panel); box-shadow: var(--shadow); }
.manage-section { margin-bottom: 24px; }
.manage-actions { display: flex; justify-content: flex-end; gap: 9px; flex-wrap: wrap; }
.roster-list { display: grid; gap: 9px; }
.roster-row { display: grid; grid-template-columns: minmax(180px, 1.4fr) minmax(160px, 1fr) auto; align-items: center; gap: 12px; padding: 13px 15px; border: 1px solid var(--line); border-radius: 12px; background: #f8fafd; }
.roster-row strong, .roster-row span { display: block; }
.roster-row small { color: var(--muted); }
.roster-actions { display: flex; gap: 7px; }
.button.compact { min-height: 36px; padding: 6px 11px; font-size: 13px; }
.button.danger { color: var(--red); background: #fff; border-color: #d9a4a4; }
.section-heading h2 { margin: 2px 0 0; font-size: 28px; }
.status-copy { min-height: 24px; color: var(--muted); }
.student-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
.student-card { width: 100%; display: grid; gap: 14px; padding: 18px; text-align: left; color: inherit; border: 1px solid var(--line); border-radius: 15px; background: #fff; }
.student-card:hover { border-color: #82a9d8; box-shadow: 0 8px 22px rgba(24,67,111,.09); }
.student-head { display: flex; align-items: start; justify-content: space-between; gap: 12px; }
.student-head strong { display: block; font-size: 19px; }
.student-head small { color: var(--muted); }
.state-pill { flex: 0 0 auto; padding: 4px 9px; border-radius: 999px; font-size: 12px; font-weight: 850; color: var(--amber); background: var(--amber-soft); }
.state-pill.done { color: var(--green); background: var(--green-soft); }
.state-pill.idle { color: var(--muted); background: #edf1f5; }
.progress-bar { height: 9px; overflow: hidden; border-radius: 99px; background: #e5edf6; }
.progress-bar span { display: block; height: 100%; border-radius: inherit; background: linear-gradient(90deg, #357cdc, #12a56c); }
.student-metrics { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.student-metrics div { padding: 9px; border-radius: 10px; background: #f5f8fc; }
.student-metrics strong { display: block; }
.student-metrics span { color: var(--muted); font-size: 12px; }
.activity-list { display: flex; align-items: center; gap: 7px; flex-wrap: wrap; padding: 9px; border-radius: 10px; background: #f5f8fc; }
.activity-list b { width: 100%; color: var(--ink); font-size: 12px; }
.activity-list em { padding: 4px 7px; border-radius: 99px; color: var(--muted); background: #fff; border: 1px solid var(--line); font-size: 11px; font-style: normal; }
.activity-list em.done { color: var(--green); background: var(--green-soft); border-color: #a8d7bf; }
.last-saved { color: var(--muted); font-size: 13px; }
.overview-card { cursor: default; }
.overview-card:hover { border-color: var(--line); box-shadow: none; }
.overview-exercises { display: grid; gap: 7px; }
.overview-exercises > span { display: flex; justify-content: space-between; gap: 10px; padding: 8px 10px; border-radius: 9px; background: #f5f8fc; }
.overview-exercises b { font-size: 13px; }
.overview-exercises em { flex: 0 0 auto; color: var(--muted); font-size: 12px; font-style: normal; font-weight: 750; }
.overview-exercises > .overview-empty { display: grid; justify-content: start; gap: 4px; padding: 14px; border: 1px dashed #aec0d4; background: #f8fafc; }
.overview-empty b { font-size: 13px; }
.overview-empty em { color: var(--muted); font-size: 12px; font-style: normal; font-weight: 650; }
.empty-state { grid-column: 1 / -1; padding: 40px 18px; text-align: center; color: var(--muted); border: 1px dashed #aec0d4; border-radius: 14px; }

dialog { width: min(920px, calc(100% - 28px)); max-height: calc(100vh - 30px); padding: clamp(20px, 4vw, 34px); border: 0; border-radius: 20px; color: var(--ink); box-shadow: 0 24px 80px rgba(10,35,67,.28); }
dialog::backdrop { background: rgba(10, 29, 52, .55); }
.form-dialog { width: min(640px, calc(100% - 28px)); }
.form-dialog form { display: grid; gap: 9px; }
.form-dialog label { margin-top: 6px; font-weight: 800; }
.form-dialog input, .form-dialog select, .form-dialog textarea { width: 100%; min-height: 46px; padding: 10px 12px; border: 1px solid #aec0d4; border-radius: 10px; color: var(--ink); background: #fff; }
.form-dialog textarea { resize: vertical; min-height: 180px; line-height: 1.65; }
.form-dialog input:focus, .form-dialog select:focus, .form-dialog textarea:focus { outline: 3px solid #7db3ff; outline-offset: 2px; }
.form-dialog input[readonly] { color: var(--muted); background: #eef3f8; }
.field-help { margin: 0; color: var(--muted); font-size: 13px; }
.import-tabs { display: grid; grid-template-columns: repeat(2, 1fr); gap: 8px; padding: 5px; border-radius: 12px; background: #eef3f8; }
.import-tab { min-height: 42px; padding: 8px 12px; border: 1px solid transparent; border-radius: 9px; color: var(--muted); background: transparent; font-weight: 850; }
.import-tab.active { color: var(--blue); border-color: #b9cee7; background: #fff; box-shadow: 0 3px 10px rgba(24,67,111,.07); }
.import-panel { display: grid; gap: 9px; padding-top: 4px; }
.student-name-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.student-name-grid > div { display: grid; gap: 6px; }
.student-name-grid label { margin: 0; }
.password-row { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 9px; }
.excel-help-card { display: grid; gap: 9px; padding: 16px; border: 1px solid #bfd2e8; border-radius: 12px; background: var(--blue-soft); }
.excel-help-card strong { font-size: 17px; }
.excel-help-card p { margin: 0; color: var(--muted); }
.excel-help-card .button { width: max-content; }
.dialog-actions { display: flex; justify-content: flex-end; gap: 10px; margin-top: 8px; }
.dialog-head { display: flex; justify-content: space-between; gap: 18px; }
.dialog-head h2 { margin: 2px 0; font-size: 30px; }
.dialog-head p { margin: 0; color: var(--muted); }
.icon-button { width: 44px; height: 44px; border: 1px solid var(--line); border-radius: 50%; color: var(--ink); background: #fff; font-size: 27px; }
.detail-summary { margin: 22px 0; display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; }
.detail-summary div { padding: 14px; border-radius: 12px; background: var(--blue-soft); }
.detail-summary strong { display: block; font-size: 24px; }
.detail-summary span { color: var(--muted); font-size: 13px; }
.day-grid { display: grid; grid-template-columns: repeat(7, minmax(0, 1fr)); gap: 10px; }
.day-card { padding: 12px 8px; text-align: center; border: 1px solid var(--line); border-radius: 12px; background: #f7f9fc; }
.day-card.complete { border-color: #91d5b4; background: var(--green-soft); }
.day-card strong, .day-card span { display: block; }
.day-card span { margin-top: 4px; color: var(--muted); font-size: 12px; }
.day-activity-list { display: grid !important; gap: 4px; margin-top: 9px !important; text-align: left; }
.day-activity-list i { display: block; padding: 4px 6px; border-radius: 7px; background: #fff; font-style: normal; }
.day-activity-list i.done { color: var(--green); background: var(--green-soft); }
.ai-analysis { margin-top: 26px; padding: 20px; border: 1px solid #b9d4f2; border-radius: 16px; background: linear-gradient(145deg, #f5f9ff, #eef6ff); }
.ai-analysis-head { display: flex; align-items: center; justify-content: space-between; gap: 18px; }
.ai-analysis-head h3 { margin: 2px 0; font-size: 24px; }
.ai-analysis-head p { margin: 0; color: var(--muted); }
.ai-analysis-panel { display: grid; gap: 14px; margin-top: 12px; }
.ai-analysis-panel > section, .ai-note-grid section { padding: 15px; border: 1px solid var(--line); border-radius: 12px; background: #fff; }
.ai-analysis-panel h4 { margin: 0 0 7px; font-size: 16px; }
.ai-analysis-panel p, .ai-analysis-panel ul { margin: 0; }
.ai-analysis-panel ul { padding-left: 22px; }
.ai-priority-list { display: grid; gap: 9px; }
.ai-priority-list article { display: grid; gap: 5px; padding: 12px; border-left: 4px solid var(--blue); border-radius: 8px; background: #f5f8fc; }
.ai-priority-list span { color: var(--muted); font-size: 14px; }
.ai-priority-list span strong { color: var(--ink); }
.ai-next-step { border-color: #9bcdb5 !important; background: var(--green-soft) !important; }
.ai-note-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.ai-disclaimer { color: var(--muted); font-size: 12px; }

@media (max-width: 800px) {
  .summary-grid { grid-template-columns: repeat(2, 1fr); }
  .student-grid { grid-template-columns: 1fr; }
  .roster-row { grid-template-columns: 1fr auto; }
  .roster-row > small { grid-column: 1 / -1; grid-row: 2; }
  .day-grid { grid-template-columns: repeat(4, 1fr); }
  .ai-analysis-head { align-items: stretch; flex-direction: column; }
}

@media (max-width: 560px) {
  .topbar { align-items: flex-start; padding: 12px 16px; }
  .brand { max-width: 64%; }
  .account-area { align-items: end; flex-direction: column; gap: 5px; font-size: 13px; }
  main { width: min(100% - 22px, 1180px); }
  .dashboard { padding-top: 28px; }
  .page-heading, .section-heading { align-items: stretch; flex-direction: column; gap: 16px; }
  .manage-actions { justify-content: stretch; }
  .manage-actions .button { flex: 1 1 100%; }
  .roster-row { grid-template-columns: 1fr; }
  .roster-actions { flex-wrap: wrap; }
  .picker-group, .class-picker { width: 100%; }
  .summary-grid { margin: 22px 0; gap: 9px; }
  .summary-card { padding: 15px; }
  .summary-card strong { font-size: 25px; }
  .student-section { padding: 16px; }
  .student-metrics { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .student-name-grid, .password-row { grid-template-columns: 1fr; }
  .password-row .button, .excel-help-card .button { width: 100%; }
  .detail-summary { grid-template-columns: repeat(2, 1fr); }
  .day-grid { grid-template-columns: repeat(2, 1fr); }
  .ai-note-grid { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; }
}