:root {
  color-scheme: dark;
  --bg: #14161a;
  --bg-elevated: #1c1f25;
  --bg-elevated-2: #23272f;
  --border: #2e333c;
  --border-strong: #3a4049;
  --text: #e7e9ec;
  --text-muted: #9aa1ab;
  --text-faint: #6b7280;
  --accent: #6ea8fe;
  --accent-strong: #4c8dfa;
  --accent-contrast: #08111f;
  --danger: #ef6f6f;
  --danger-bg: rgba(239, 111, 111, 0.1);
  --success: #63c988;
  --warn: #e0b354;
  --chip-bg: #23272f;
  --chip-border: #343a44;
  --radius: 10px;
  --radius-lg: 14px;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 4px 16px rgba(0, 0, 0, 0.24);
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue",
    Arial, sans-serif;
  font-size: 15px;
  line-height: 1.45;
}

button, input, textarea {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
}

a {
  color: var(--accent);
}

.content {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 20px 40px;
}

/* ---------- Header ---------- */

.topbar {
  max-width: 900px;
  margin: 0 auto;
  padding: 24px 20px 16px;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.topbar-title h1 {
  font-size: 20px;
  margin: 0 0 4px;
}

.progress-count {
  margin: 0;
  color: var(--text-muted);
  font-size: 13px;
}

.topbar-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

/* ---------- Buttons ---------- */

.btn {
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  border-radius: var(--radius);
  padding: 8px 14px;
  cursor: pointer;
  white-space: nowrap;
  transition: background-color 0.15s, border-color 0.15s;
}

.btn:hover {
  background: var(--bg-elevated-2);
}

.btn:active {
  background: var(--border);
}

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-contrast);
  font-weight: 600;
}

.btn-primary:hover {
  background: var(--accent-strong);
  border-color: var(--accent-strong);
}

.btn-ghost {
  background: transparent;
}

.btn-icon {
  background: transparent;
  padding: 8px 11px;
  font-size: 16px;
  line-height: 1;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ---------- Banner ---------- */

.banner {
  max-width: 900px;
  margin: 0 auto 16px;
  padding: 12px 20px;
}

.banner-inner {
  background: var(--danger-bg);
  border: 1px solid var(--danger);
  color: var(--text);
  border-radius: var(--radius);
  padding: 12px 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.banner.info .banner-inner {
  background: rgba(110, 168, 254, 0.1);
  border-color: var(--accent);
}

.banner-inner button {
  flex-shrink: 0;
}

/* ---------- Toolbar / filters ---------- */

.toolbar {
  margin-bottom: 20px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.status-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.chip {
  border: 1px solid var(--chip-border);
  background: var(--chip-bg);
  color: var(--text-muted);
  border-radius: 999px;
  padding: 6px 12px;
  font-size: 13px;
  cursor: pointer;
  transition: background-color 0.15s, border-color 0.15s, color 0.15s;
}

.chip:hover {
  border-color: var(--border-strong);
}

.chip[aria-pressed="true"] {
  color: var(--text);
  border-color: var(--accent);
  background: rgba(110, 168, 254, 0.14);
}

.toolbar-row {
  display: flex;
  gap: 8px;
}

.search-input {
  flex: 1;
  min-width: 0;
  background: var(--bg-elevated);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  padding: 8px 12px;
}

.search-input:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
}

.settings-panel {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 10px 12px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-size: 13px;
  color: var(--text-muted);
}

.settings-option {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
}

/* ---------- Card list ---------- */

.card-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.empty-state, .auth-state {
  background: var(--bg-elevated);
  border: 1px dashed var(--border-strong);
  border-radius: var(--radius-lg);
  padding: 32px 20px;
  text-align: center;
  color: var(--text-muted);
}

.empty-state p, .auth-state p {
  margin: 0 0 12px;
}

.card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px;
  box-shadow: var(--shadow);
}

.card.overdue {
  border-color: var(--danger);
  box-shadow: 0 0 0 1px var(--danger), var(--shadow);
}

.card-heading {
  display: flex;
  align-items: baseline;
  gap: 10px;
  flex-wrap: wrap;
}

.card-date {
  font-size: 16px;
  margin: 0;
}

.card-filename {
  margin: 0;
  color: var(--text-faint);
  font-size: 12px;
}

.card-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 8px 0 12px;
  font-size: 13px;
  color: var(--text-muted);
}

.card-link {
  text-decoration: none;
}

.card-link:hover {
  text-decoration: underline;
}

.status-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.status-chip {
  border: 1px solid var(--chip-border);
  background: var(--chip-bg);
  color: var(--text-muted);
  border-radius: 999px;
  padding: 6px 12px;
  font-size: 13px;
  cursor: pointer;
}

.status-chip[aria-pressed="true"][data-status="todo"] {
  border-color: var(--text-faint);
  color: var(--text);
  background: var(--bg-elevated-2);
}

.status-chip[aria-pressed="true"][data-status="in_progress"] {
  border-color: var(--warn);
  color: var(--warn);
  background: rgba(224, 179, 84, 0.12);
}

.status-chip[aria-pressed="true"][data-status="done"] {
  border-color: var(--success);
  color: var(--success);
  background: rgba(99, 201, 136, 0.12);
}

.status-chip[aria-pressed="true"][data-status="reviewed"] {
  border-color: var(--accent);
  color: var(--accent);
  background: rgba(110, 168, 254, 0.14);
}

.card-note {
  margin-top: 12px;
  border-top: 1px solid var(--border);
  padding-top: 10px;
}

.card-note summary {
  cursor: pointer;
  color: var(--text-muted);
  font-size: 13px;
}

.card-note-body {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 10px;
}

.note-field {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 12px;
  color: var(--text-muted);
}

.note-deadline, .note-text {
  background: var(--bg);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  padding: 8px 10px;
  color: var(--text);
  resize: vertical;
}

.note-deadline {
  width: max-content;
}

.note-deadline:focus, .note-text:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
}

.tutor-note {
  background: rgba(110, 168, 254, 0.08);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
  padding: 8px 10px;
  font-size: 13px;
}

.tutor-note strong {
  display: block;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--accent);
  margin-bottom: 4px;
}

.tutor-note p {
  margin: 0;
  white-space: pre-wrap;
}

.status-line {
  margin: 4px 0 12px;
  font-size: 13px;
  color: var(--text-muted);
}

.student-note-box {
  margin-bottom: 12px;
}

/* ---------- Skeletons ---------- */

.card-skeleton {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.skeleton-line {
  border-radius: 6px;
  background: linear-gradient(90deg, var(--bg-elevated-2) 25%, var(--border) 37%, var(--bg-elevated-2) 63%);
  background-size: 400% 100%;
  animation: shimmer 1.4s ease infinite;
}

.skeleton-title {
  width: 40%;
  height: 16px;
}

.skeleton-sub {
  width: 65%;
  height: 12px;
}

.skeleton-chips {
  width: 90%;
  height: 26px;
}

@keyframes shimmer {
  0% { background-position: 100% 0; }
  100% { background-position: -100% 0; }
}

/* ---------- Footer ---------- */

.footer {
  max-width: 900px;
  margin: 0 auto;
  padding: 20px;
  display: flex;
  gap: 10px;
  justify-content: center;
  border-top: 1px solid var(--border);
}

/* ---------- Responsive ---------- */

@media (max-width: 480px) {
  .topbar {
    flex-direction: column;
    align-items: stretch;
  }

  .topbar-actions {
    justify-content: stretch;
  }

  .topbar-actions .btn {
    flex: 1;
  }

  .card-meta {
    flex-wrap: wrap;
  }

  .footer {
    flex-direction: column;
  }
}