/* ---- design tokens ---- */
:root {
  --color-primary:      #0078d4;
  --color-primary-dark: #005a9e;
  --color-primary-bg:   #eff6fc;
  --color-danger:       #c4262e;
  --color-danger-bg:    #fef0f1;
  --color-success:      #107c10;

  --color-bg:           #faf9f8;
  --color-surface:      #ffffff;
  --color-border:       #e1dfdd;
  --color-border-light: #f0eeec;

  --color-text:         #201f1e;
  --color-text-muted:   #605e5c;
  --color-text-subtle:  #a19f9d;

  --header-height:      52px;
  --sidebar-width:      220px;

  --radius:  4px;
  --radius-lg: 8px;
  --shadow:  0 1px 4px rgba(0,0,0,.1);
  --shadow-lg: 0 4px 16px rgba(0,0,0,.12);

  --font-sans: 'Segoe UI', system-ui, -apple-system, sans-serif;
  --font-mono: 'Cascadia Code', 'Consolas', 'Courier New', monospace;
}

/* ---- reset ---- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; }
body {
  font-family: var(--font-sans);
  font-size: 14px;
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.5;
}
a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }
ul { list-style: none; }
button { cursor: pointer; font: inherit; }

/* ---- header ---- */
.header {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--header-height);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  z-index: 100;
  box-shadow: var(--shadow);
}
.header-inner {
  display: flex;
  align-items: center;
  gap: 12px;
  height: 100%;
  padding: 0 20px;
}
.logo {
  font-size: 16px;
  font-weight: 600;
  color: var(--color-primary);
  white-space: nowrap;
}
.course-name-input {
  flex: 1;
  min-width: 0;
  max-width: 400px;
  height: 32px;
  padding: 0 10px;
  font-size: 15px;
  font-weight: 600;
  color: var(--color-text);
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius);
  transition: border-color .15s, background .15s;
}
.course-name-input:hover { border-color: var(--color-border); }
.course-name-input:focus {
  outline: none;
  border-color: var(--color-primary);
  background: var(--color-surface);
}
.header-actions { display: flex; align-items: center; gap: 8px; margin-left: auto; }

/* ---- main content area ---- */
.main {
  margin-top: var(--header-height);
  padding: 32px 24px;
  max-width: 1100px;
  margin-left: auto;
  margin-right: auto;
}

/* ---- page heading ---- */
.page-heading {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 24px;
}
.page-heading h2 { font-size: 22px; font-weight: 600; }
.count { font-size: 13px; color: var(--color-text-muted); }

/* ---- course grid ---- */
.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

/* ---- card ---- */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: box-shadow .2s;
}
.card:hover { box-shadow: var(--shadow-lg); }
.card-body { padding: 16px; flex: 1; }
.card-title { font-size: 15px; font-weight: 600; margin-bottom: 6px; }
.card-desc {
  font-size: 13px;
  color: var(--color-text-muted);
  margin-bottom: 10px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 12px;
  color: var(--color-text-subtle);
}
.meta-tag {
  background: var(--color-primary-bg);
  color: var(--color-primary);
  padding: 2px 8px;
  border-radius: 10px;
}
.card-actions {
  display: flex;
  gap: 6px;
  padding: 10px 14px;
  border-top: 1px solid var(--color-border-light);
  background: var(--color-bg);
}

/* ---- empty state ---- */
.empty-state {
  text-align: center;
  padding: 64px 24px;
  color: var(--color-text-muted);
}
.empty-icon { font-size: 48px; margin-bottom: 16px; }
.empty-text { font-size: 16px; font-weight: 500; margin-bottom: 6px; color: var(--color-text); }
.empty-sub { font-size: 13px; margin-bottom: 20px; }

/* ---- editor layout ---- */
.editor-layout {
  display: flex;
  height: calc(100vh - var(--header-height));
  margin-top: var(--header-height);
  overflow: hidden;
}

/* ---- sidebar ---- */
.sidebar {
  width: var(--sidebar-width);
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  flex-shrink: 0;
}
.sidebar-heading {
  padding: 14px 16px 8px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--color-text-subtle);
}
.theme-list { flex: 1; padding: 4px 8px; }
.theme-item {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 10px;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background .15s;
}
.theme-item:hover { background: var(--color-bg); }
.theme-item.is-active {
  background: var(--color-primary-bg);
  color: var(--color-primary);
  font-weight: 500;
}
.theme-item-title {
  flex: 1;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  font-size: 13px;
}
.sidebar-add {
  margin: 8px;
  width: calc(100% - 16px);
  justify-content: center;
}

/* ---- editor main ---- */
.editor-main {
  flex: 1;
  overflow-y: auto;
  background: var(--color-bg);
}
.theme-editor { padding: 24px; max-width: 820px; }
.theme-meta { margin-bottom: 20px; display: flex; flex-direction: column; gap: 10px; }

/* ---- tabs ---- */
.tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--color-border);
  margin-bottom: 20px;
}
.tab {
  padding: 8px 18px;
  font-size: 14px;
  font-weight: 500;
  color: var(--color-text-muted);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: color .15s, border-color .15s;
  display: flex;
  align-items: center;
  gap: 6px;
}
.tab:hover { color: var(--color-text); }
.tab.is-active { color: var(--color-primary); border-bottom-color: var(--color-primary); }

/* ---- item list ---- */
.item-list { display: flex; flex-direction: column; gap: 8px; }
.btn-add-item {
  margin-top: 4px;
  justify-content: center;
  border: 1px dashed var(--color-border);
  border-radius: var(--radius);
  padding: 8px;
  width: 100%;
}
.btn-add-item:hover { border-color: var(--color-primary); color: var(--color-primary); }

/* ---- item row ---- */
.item-row {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.item-row.is-open { border-color: var(--color-primary); }
.item-row-head {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
}
.item-num {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--color-bg);
  color: var(--color-text-muted);
  font-size: 12px;
  font-weight: 600;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.item-row-label {
  flex: 1;
  min-width: 0;
  font-size: 14px;
  font-weight: 500;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.item-row-btns { display: flex; gap: 4px; flex-shrink: 0; }

/* ---- item form ---- */
.item-form {
  padding: 16px;
  border-top: 1px solid var(--color-border-light);
  background: var(--color-bg);
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.toolbar { display: flex; gap: 8px; }

/* ---- task list (in mission form) ---- */
.task-list { display: flex; flex-direction: column; gap: 6px; }
.task-row { display: flex; align-items: center; gap: 8px; }
.task-num {
  width: 20px;
  text-align: right;
  color: var(--color-text-subtle);
  font-size: 12px;
  flex-shrink: 0;
}
.task-row .input { flex: 1; }

/* ---- buttons ---- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 0 14px;
  height: 32px;
  font-size: 13px;
  font-weight: 500;
  border-radius: var(--radius);
  border: 1px solid transparent;
  transition: background .15s, border-color .15s, opacity .15s;
  white-space: nowrap;
  cursor: pointer;
  user-select: none;
}
.btn:disabled { opacity: .5; cursor: default; }

.btn-primary {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}
.btn-primary:hover:not(:disabled) { background: var(--color-primary-dark); border-color: var(--color-primary-dark); }

.btn-ghost {
  background: transparent;
  color: var(--color-text);
  border-color: var(--color-border);
}
.btn-ghost:hover:not(:disabled) { background: var(--color-bg); }

.btn-danger {
  background: var(--color-danger-bg);
  color: var(--color-danger);
  border-color: var(--color-danger);
}
.btn-danger:hover:not(:disabled) { background: var(--color-danger); color: #fff; }

.btn-sm { height: 28px; padding: 0 10px; font-size: 12px; }
.btn-full { width: 100%; }

/* icon-only button */
.btn-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: var(--radius);
  border: none;
  background: transparent;
  color: var(--color-text-muted);
  font-size: 14px;
  transition: background .15s, color .15s;
  cursor: pointer;
  flex-shrink: 0;
}
.btn-icon:hover:not(:disabled) { background: var(--color-bg); color: var(--color-text); }
.btn-icon:disabled { opacity: .3; cursor: default; }
.btn-icon.is-danger:hover { background: var(--color-danger-bg); color: var(--color-danger); }
.btn-icon.is-muted { opacity: 0; transition: opacity .15s; }
.theme-item:hover .btn-icon.is-muted { opacity: 1; }

/* ---- form elements ---- */
.input {
  width: 100%;
  height: 34px;
  padding: 0 10px;
  font: inherit;
  font-size: 14px;
  color: var(--color-text);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: border-color .15s;
}
.input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 2px rgba(0,120,212,.15);
}
.input-lg { height: 40px; font-size: 16px; font-weight: 600; }

.textarea {
  width: 100%;
  padding: 8px 10px;
  font: inherit;
  font-size: 14px;
  color: var(--color-text);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  resize: vertical;
  transition: border-color .15s;
  line-height: 1.6;
}
.textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 2px rgba(0,120,212,.15);
}
.textarea.is-code {
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.5;
}

.label {
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-muted);
}

/* ---- badge ---- */
.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 18px;
  height: 18px;
  padding: 0 5px;
  border-radius: 9px;
  font-size: 11px;
  font-weight: 700;
  background: var(--color-bg);
  color: var(--color-text-muted);
}
.tab.is-active .badge {
  background: var(--color-primary-bg);
  color: var(--color-primary);
}