/* ==========================================================
   設計 tokens ── 靈感來自「課程講義／圖書卡片目錄」的檔案感
   ========================================================== */
:root {
  --ink:        #16324F;   /* 主要文字／標題,深墨藍 */
  --ink-soft:   #4A5A6A;   /* 次要文字 */
  --paper:      #EDEAE1;   /* 頁面背景,暖石紙色 */
  --paper-raised: #FAF8F3; /* 卡片背景,略亮於頁面 */
  --brass:      #B8874F;   /* 主要強調色,黃銅 */
  --brass-dark: #96693A;
  --sage:       #6E8B6E;   /* 次要強調色,頁內顯示標記 */
  --line:       #D9D2C2;   /* 分隔線 */
  --line-strong:#C7BEA8;
  --danger:     #A64B3F;

  --tab-1: #B8874F; /* 分類色帶輪替 */
  --tab-2: #6E8B6E;
  --tab-3: #7C6FA6;
  --tab-4: #4E7C97;
  --tab-5: #A65D6B;

  --font-display: "Source Serif 4", Georgia, "Noto Serif TC", serif;
  --font-body: "IBM Plex Sans", "Noto Sans TC", -apple-system, sans-serif;
  --font-mono: "IBM Plex Mono", "Noto Sans Mono", monospace;

  --sidebar-w: 264px;
  --radius: 3px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  -webkit-font-smoothing: antialiased;
}

button { font-family: inherit; cursor: pointer; }
input, textarea { font-family: inherit; }

/* focus visibility */
a:focus-visible, button:focus-visible, input:focus-visible, textarea:focus-visible {
  outline: 2px solid var(--brass-dark);
  outline-offset: 2px;
}

/* ==========================================================
   版面
   ========================================================== */
.app {
  display: flex;
  min-height: 100vh;
  align-items: stretch;
}

/* ---------- 側邊欄 ---------- */
.sidebar {
  width: var(--sidebar-w);
  flex: 0 0 var(--sidebar-w);
  background: var(--ink);
  color: var(--paper);
  display: flex;
  flex-direction: column;
  transition: margin-left .28s ease, opacity .2s ease;
  position: relative;
}
.sidebar.is-collapsed {
  margin-left: calc(-1 * var(--sidebar-w));
  opacity: 0;
  pointer-events: none;
}

.sidebar-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 18px 14px;
  border-bottom: 1px solid rgba(237,234,225,0.14);
}
.brand { display: flex; align-items: baseline; gap: 8px; }
.brand-mark {
  font-family: var(--font-display);
  font-size: 22px;
  color: var(--brass);
}
.brand-text {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: rgba(237,234,225,0.8);
}

.icon-btn {
  background: transparent;
  border: 1px solid rgba(237,234,225,0.3);
  color: inherit;
  border-radius: var(--radius);
  width: 30px;
  height: 30px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  text-decoration: none;
}
.icon-btn:hover { border-color: var(--brass); color: var(--brass); }

.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 10px 0 6px;
}

.nav-group { margin-bottom: 4px; }
.nav-group-label {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--brass);
  padding: 14px 18px 6px;
  border-top: 1px dashed rgba(237,234,225,0.16);
  margin-top: 6px;
}
.nav-group:first-child .nav-group-label { border-top: none; margin-top: 0; }

.nav-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 6px;
  padding: 9px 14px 9px 8px;
  color: rgba(237,234,225,0.92);
  text-decoration: none;
  font-size: 14px;
  border-left: 2px solid transparent;
}
.nav-item:hover { background: rgba(184,135,79,0.14); border-left-color: var(--brass); }
.nav-item.is-hidden-item { opacity: .5; }
.nav-item.is-dragging { opacity: .35; }

.nav-drag-handle {
  flex: 0 0 auto;
  color: rgba(237,234,225,0.35);
  font-size: 13px;
  padding: 2px 2px;
  cursor: grab;
  touch-action: none;
}
.nav-drag-handle:hover { color: var(--brass); }

.nav-item .nav-item-label {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 1;
  min-width: 0;
  color: rgba(237,234,225,0.92);
  text-decoration: none;
}
.nav-item .nav-item-label:visited { color: rgba(237,234,225,0.92); }
.nav-item .nav-item-label:hover { color: var(--brass); text-decoration: none; }
.nav-item .nav-item-label span.title {
  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.mode-dot {
  width: 6px; height: 6px; border-radius: 50%; flex: 0 0 auto;
}
.mode-dot.newtab { background: var(--brass); }
.mode-dot.iframe { background: var(--sage); }

.nav-item-actions {
  display: flex;
  align-items: center;
  gap: 2px;
  flex: 0 0 auto;
}
.nav-item-action {
  background: transparent;
  border: none;
  color: rgba(237,234,225,0.5);
  font-size: 11.5px;
  padding: 3px 4px;
  font-family: var(--font-mono);
}
.nav-item-action:hover { color: var(--brass); }
.nav-item-action.danger:hover { color: var(--danger); }

.hidden-tag {
  font-family: var(--font-mono);
  font-size: 9.5px;
  letter-spacing: .04em;
  color: rgba(237,234,225,0.5);
  border: 1px solid rgba(237,234,225,0.3);
  border-radius: 20px;
  padding: 1px 6px;
  flex: 0 0 auto;
}

.nav-empty {
  padding: 10px 18px;
  font-size: 13px;
  color: rgba(237,234,225,0.55);
}

.sidebar-teacher {
  padding: 14px 18px 6px;
  border-top: 1px solid rgba(237,234,225,0.14);
}
.sidebar-teacher form { display: flex; flex-direction: column; gap: 8px; }
.sidebar-teacher input {
  background: rgba(237,234,225,0.08);
  border: 1px solid rgba(237,234,225,0.25);
  color: var(--paper);
  border-radius: var(--radius);
  padding: 7px 9px;
  font-size: 13px;
}
.sidebar-teacher input::placeholder { color: rgba(237,234,225,0.45); }
.sidebar-teacher .mode-choice { color: rgba(237,234,225,0.8); font-size: 12.5px; }
.sidebar-teacher .hidden-choice { color: rgba(237,234,225,0.75); font-size: 12px; display: flex; align-items: center; gap: 6px; }
.sidebar-teacher .form-btn-row { display: flex; gap: 8px; }
.sidebar-teacher .form-btn-row .btn { flex: 1; }

.panel-label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--brass);
  margin: 0 0 8px;
}

.sidebar-foot {
  padding: 14px 18px 20px;
}

/* 收合後浮動的展開按鈕 */
.sidebar-show {
  position: fixed;
  left: 14px;
  top: 18px;
  z-index: 20;
  width: 38px;
  height: 38px;
  border-radius: var(--radius);
  border: 1px solid var(--line-strong);
  background: var(--paper-raised);
  color: var(--ink);
  font-size: 16px;
  box-shadow: 0 2px 6px rgba(22,50,79,0.12);
}
.sidebar-show:hover { border-color: var(--brass); color: var(--brass-dark); }

/* ---------- 主要內容 ---------- */
.main {
  flex: 1;
  min-width: 0;
  padding: 34px 40px 60px;
}

.topbar {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  border-bottom: 2px solid var(--ink);
  padding-bottom: 16px;
  margin-bottom: 26px;
  flex-wrap: wrap;
  gap: 12px;
}
.topbar h1 {
  font-family: var(--font-display);
  font-size: 34px;
  margin: 0 0 4px;
  font-weight: 600;
}
.topbar-sub {
  margin: 0;
  color: var(--ink-soft);
  font-size: 14px;
  font-family: var(--font-mono);
  letter-spacing: .02em;
}
.badge {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .08em;
  text-transform: uppercase;
  background: var(--brass);
  color: var(--paper-raised);
  padding: 5px 10px;
  border-radius: 20px;
}

/* ---------- 講師面板 ---------- */
.teacher-panel { margin-bottom: 28px; }
.panel-card {
  background: var(--paper-raised);
  border: 1px solid var(--line-strong);
  border-left: 3px solid var(--brass);
  border-radius: var(--radius);
  padding: 18px 20px;
}
.panel-card form {
  display: grid;
  grid-template-columns: 1.3fr 1fr;
  gap: 10px 12px;
}
.panel-card form input,
.panel-card form textarea {
  border: 1px solid var(--line-strong);
  background: #fff;
  border-radius: var(--radius);
  padding: 9px 10px;
  font-size: 14px;
  color: var(--ink);
}
.panel-card form textarea { grid-column: 1 / -1; resize: vertical; }
.panel-card form .mode-choice { grid-column: 1 / -1; display: flex; gap: 18px; font-size: 13.5px; color: var(--ink-soft); }
.panel-card form .hidden-choice {
  grid-column: 1 / -1;
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13.5px;
  color: var(--ink-soft);
}
.panel-card form .form-btn-row { grid-column: 1 / -1; display: flex; gap: 10px; }

.form-msg {
  margin: 10px 0 0;
  font-size: 13px;
}
.form-msg.ok { color: var(--sage); }
.form-msg.err { color: var(--danger); }

/* ---------- 按鈕 ---------- */
.btn {
  border: none;
  border-radius: var(--radius);
  padding: 9px 16px;
  font-size: 13.5px;
  font-weight: 500;
}
.btn-brass { background: var(--brass); color: #fff; }
.btn-brass:hover { background: var(--brass-dark); }
.btn-ghost { background: transparent; border: 1px solid var(--line-strong); color: var(--ink); }
.btn-ghost:hover { border-color: var(--brass); color: var(--brass-dark); }
.sidebar .btn-ghost { border-color: rgba(237,234,225,0.35); color: var(--paper); }
.sidebar .btn-ghost:hover { border-color: var(--brass); color: var(--brass); }

/* ---------- 課程看板／卡片 (卡片目錄風格) ---------- */
.course-board { display: flex; flex-direction: column; gap: 26px; }

.board-group-label {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--ink-soft);
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
}
.board-group-label::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--line-strong);
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(258px, 1fr));
  gap: 16px;
}

.course-card {
  position: relative;
  background: var(--paper-raised);
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  padding: 18px 16px 16px 20px;
  text-decoration: none;
  color: var(--ink);
  display: flex;
  flex-direction: column;
  gap: 8px;
  transition: transform .12s ease, box-shadow .12s ease;
  --tab-color: var(--brass);
}
.course-card::before {
  content: "";
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 5px;
  background: var(--tab-color);
  border-radius: var(--radius) 0 0 var(--radius);
}
.course-card::after {
  content: "";
  position: absolute;
  left: -3px;
  top: 16px;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--paper);
  border: 1.5px solid var(--tab-color);
}
.course-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(22,50,79,0.12);
  border-color: var(--tab-color);
}
.course-card.is-hidden-item { opacity: .55; }
.course-card.is-dragging { opacity: .35; }

.card-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 8px;
}
.card-top-left {
  display: flex;
  align-items: center;
  gap: 6px;
  min-width: 0;
}
.card-drag-handle {
  color: var(--ink-soft);
  opacity: .5;
  font-size: 13px;
  cursor: grab;
  touch-action: none;
  flex: 0 0 auto;
}
.card-drag-handle:hover { opacity: 1; color: var(--tab-color); }
.card-index {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--ink-soft);
  letter-spacing: .04em;
}
.card-actions {
  display: flex;
  align-items: center;
  gap: 2px;
  flex: 0 0 auto;
}
.card-action {
  background: transparent;
  border: none;
  color: var(--ink-soft);
  font-size: 12px;
  line-height: 1;
  padding: 2px 5px;
  font-family: var(--font-mono);
}
.card-action:hover { color: var(--brass-dark); }
.card-action.danger:hover { color: var(--danger); }

.card-hidden-tag {
  align-self: flex-start;
  font-family: var(--font-mono);
  font-size: 9.5px;
  letter-spacing: .04em;
  color: var(--ink-soft);
  border: 1px solid var(--line-strong);
  border-radius: 20px;
  padding: 1px 7px;
}

.card-title {
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 600;
  margin: 0;
  line-height: 1.35;
}
.card-desc {
  font-size: 13px;
  color: var(--ink-soft);
  line-height: 1.5;
  margin: 0;
}
.card-foot {
  margin-top: auto;
  display: flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--ink-soft);
  text-transform: uppercase;
  letter-spacing: .06em;
}

.board-empty {
  color: var(--ink-soft);
  font-size: 14px;
  border: 1px dashed var(--line-strong);
  border-radius: var(--radius);
  padding: 20px;
  text-align: center;
}

/* ==========================================================
   Modal
   ========================================================== */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(22,50,79,0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  padding: 20px;
}
.modal[hidden] { display: none; }

.modal-box {
  background: var(--paper-raised);
  border-radius: var(--radius);
  border-top: 3px solid var(--brass);
  padding: 26px 24px;
  width: 100%;
  max-width: 320px;
  box-shadow: 0 20px 50px rgba(22,50,79,0.28);
}
.modal-box h3 {
  font-family: var(--font-display);
  margin: 0 0 14px;
}
.modal-box input {
  width: 100%;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  padding: 10px 12px;
  font-size: 14px;
}
.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 10px;
  margin-top: 16px;
}
.error { color: var(--danger); font-size: 13px; margin: 10px 0 0; }

.viewer .viewer-box {
  background: var(--paper-raised);
  width: min(1000px, 100%);
  height: min(80vh, 720px);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  box-shadow: 0 20px 60px rgba(22,50,79,0.35);
}
.viewer-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 13px;
}
.viewer-head-actions { display: flex; gap: 8px; }
.viewer-head .icon-btn { border-color: rgba(237,234,225,0.3); color: var(--paper); width: 26px; height: 26px; font-size: 12px; }
.viewer-head .icon-btn:hover { border-color: var(--brass); color: var(--brass); }
.viewer-box iframe {
  flex: 1;
  border: none;
  width: 100%;
  background: #fff;
}

/* ==========================================================
   RWD
   ========================================================== */
@media (max-width: 860px) {
  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    z-index: 30;
    box-shadow: 0 0 0 100vmax rgba(0,0,0,0);
  }
  .sidebar:not(.is-collapsed) {
    box-shadow: 0 0 0 100vmax rgba(22,50,79,0.35);
  }
  .main { padding: 22px 18px 50px; }
  .panel-card form { grid-template-columns: 1fr; }
  .topbar h1 { font-size: 26px; }
}

@media (prefers-reduced-motion: reduce) {
  .sidebar, .course-card { transition: none; }
}