/* ============================================
   Padlet Classrooms — refined design system
   ============================================ */

:root {
  --background: #fafaf9;
  --background-pattern: radial-gradient(1200px 600px at 10% -10%, rgba(124, 58, 237, 0.08), transparent 60%),
                        radial-gradient(900px 500px at 100% 0%, rgba(236, 72, 153, 0.06), transparent 55%),
                        linear-gradient(180deg, #fafaf9 0%, #f4f4f5 100%);
  --foreground: #0a0a0a;
  --foreground-soft: #27272a;
  --surface: #ffffff;
  --surface-2: #f4f4f5;
  --surface-3: #e4e4e7;
  --border: #e4e4e7;
  --border-strong: #d4d4d8;
  --muted: #71717a;
  --accent: #7c3aed;
  --accent-hover: #6d28d9;
  --accent-soft: rgba(124, 58, 237, 0.10);
  --success: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
  --shadow-sm: 0 1px 2px rgba(15, 15, 25, 0.04);
  --shadow: 0 1px 2px rgba(15, 15, 25, 0.04), 0 4px 12px rgba(15, 15, 25, 0.06);
  --shadow-lg: 0 8px 24px rgba(15, 15, 25, 0.08), 0 24px 48px rgba(15, 15, 25, 0.10);
  --shadow-card: 0 1px 2px rgba(15, 15, 25, 0.04), 0 2px 8px rgba(15, 15, 25, 0.05);
  --header-bg: rgba(255, 255, 255, 0.78);
  --radius: 12px;
  --radius-lg: 16px;
}

.dark {
  --background: #09090b;
  --background-pattern: radial-gradient(1200px 600px at 10% -10%, rgba(124, 58, 237, 0.18), transparent 60%),
                        radial-gradient(900px 500px at 100% 0%, rgba(236, 72, 153, 0.10), transparent 55%),
                        linear-gradient(180deg, #09090b 0%, #0c0c0f 100%);
  --foreground: #fafafa;
  --foreground-soft: #d4d4d8;
  --surface: #18181b;
  --surface-2: #27272a;
  --surface-3: #3f3f46;
  --border: #27272a;
  --border-strong: #3f3f46;
  --muted: #a1a1aa;
  --accent: #a78bfa;
  --accent-hover: #8b5cf6;
  --accent-soft: rgba(167, 139, 250, 0.14);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.5), 0 24px 48px rgba(0, 0, 0, 0.5);
  --shadow-card: 0 1px 2px rgba(0, 0, 0, 0.3), 0 2px 8px rgba(0, 0, 0, 0.35);
  --header-bg: rgba(15, 15, 18, 0.72);
}

* { box-sizing: border-box; }
*:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}
html, body { height: 100%; margin: 0; }
body {
  background-color: var(--background);
  background-image: var(--background-pattern);
  background-attachment: fixed;
  color: var(--foreground);
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 15px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  position: relative;
  overflow-x: hidden;
}

/* Drifting gradient orbs — purely decorative, sit behind everything */
body::before,
body::after {
  content: "";
  position: fixed;
  border-radius: 50%;
  filter: blur(90px);
  opacity: 0.55;
  pointer-events: none;
  z-index: -1;
  will-change: transform;
}
body::before {
  width: 520px;
  height: 520px;
  top: -160px;
  left: -120px;
  background: radial-gradient(circle, rgba(124, 58, 237, 0.45), transparent 70%);
  animation: orb-drift-1 22s ease-in-out infinite alternate;
}
body::after {
  width: 600px;
  height: 600px;
  bottom: -200px;
  right: -180px;
  background: radial-gradient(circle, rgba(236, 72, 153, 0.35), transparent 70%);
  animation: orb-drift-2 28s ease-in-out infinite alternate;
}
.dark body::before { background: radial-gradient(circle, rgba(167, 139, 250, 0.45), transparent 70%); opacity: 0.45; }
.dark body::after  { background: radial-gradient(circle, rgba(236, 72, 153, 0.30), transparent 70%); opacity: 0.40; }

@keyframes orb-drift-1 {
  0%   { transform: translate3d(0, 0, 0) scale(1); }
  50%  { transform: translate3d(60px, 80px, 0) scale(1.08); }
  100% { transform: translate3d(120px, 30px, 0) scale(1.04); }
}
@keyframes orb-drift-2 {
  0%   { transform: translate3d(0, 0, 0) scale(1); }
  50%  { transform: translate3d(-80px, -60px, 0) scale(1.06); }
  100% { transform: translate3d(-30px, -120px, 0) scale(1.10); }
}
button { font: inherit; cursor: pointer; }
input, textarea, select { font: inherit; color: inherit; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* The [hidden] attribute should always win over display rules */
[hidden] { display: none !important; }

/* ============================================
   Header
   ============================================ */
.app-header {
  background: var(--header-bg);
  backdrop-filter: saturate(180%) blur(16px);
  -webkit-backdrop-filter: saturate(180%) blur(16px);
  border-bottom: 1px solid var(--border);
  padding: 14px 28px;
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.header-row-main {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 1;
  min-width: 0;
}
.header-row-controls {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.app-header h1 {
  margin: 0;
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--foreground);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
#board-title-edit { font-size: 14px; }

.exit-room-btn {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--foreground);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 13px;
  font-weight: 600;
  margin-right: 4px;
  flex-shrink: 0;
}
.exit-room-btn:hover {
  background: var(--accent-soft);
  color: var(--accent);
  border-color: var(--accent);
}

.online-status {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  font-weight: 500;
  color: var(--muted);
  padding: 5px 11px;
  border-radius: 999px;
  background: var(--surface-2);
  border: 1px solid var(--border);
}
.online-dot {
  width: 7px; height: 7px;
  border-radius: 999px;
  background: var(--success);
  box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.18);
}
.online-status.offline .online-dot {
  background: var(--danger);
  box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.18);
}

.user-area { display: flex; align-items: center; gap: 8px; }
.user-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 4px 12px 4px 4px;
  border-radius: 999px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  font-size: 13px;
  font-weight: 600;
}
.avatar {
  width: 28px; height: 28px;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--accent), #ec4899);
  color: white;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  font-weight: 700;
  overflow: hidden;
  letter-spacing: 0.02em;
}
.avatar img { width: 100%; height: 100%; object-fit: cover; }
.admin-badge {
  font-size: 10px;
  background: var(--accent);
  color: white;
  padding: 2px 6px;
  border-radius: 999px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

/* ============================================
   Buttons
   ============================================ */
.btn {
  background: var(--accent);
  color: white;
  border: none;
  padding: 9px 18px;
  border-radius: 10px;
  font-weight: 600;
  font-size: 14px;
  letter-spacing: -0.005em;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: background 0.15s ease, transform 0.1s ease, box-shadow 0.15s ease;
  box-shadow: 0 1px 2px rgba(124, 58, 237, 0.18);
}
.btn:hover { background: var(--accent-hover); box-shadow: 0 4px 12px rgba(124, 58, 237, 0.28); }
.btn:active { transform: translateY(1px); box-shadow: 0 1px 2px rgba(124, 58, 237, 0.18); }
.btn:disabled { opacity: 0.55; cursor: not-allowed; box-shadow: none; }
.btn-secondary {
  background: var(--surface);
  color: var(--foreground);
  border: 1px solid var(--border-strong);
  box-shadow: var(--shadow-sm);
}
.btn-secondary:hover { background: var(--surface-2); box-shadow: var(--shadow); }
.btn-danger { background: var(--danger); box-shadow: 0 1px 2px rgba(239, 68, 68, 0.2); }
.btn-danger:hover { background: #dc2626; box-shadow: 0 4px 12px rgba(239, 68, 68, 0.3); }
.btn-icon {
  width: 36px; height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  border-radius: 10px;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--foreground);
  box-shadow: none;
}
.btn-icon:hover { background: var(--surface-2); }
.btn-ghost {
  background: transparent;
  border: none;
  color: var(--muted);
  padding: 6px 10px;
  border-radius: 8px;
  box-shadow: none;
  font-weight: 500;
}
.btn-ghost:hover { background: var(--surface-2); color: var(--foreground); }

/* ============================================
   Announcement banner
   ============================================ */
.announcement {
  background: linear-gradient(135deg, rgba(124, 58, 237, 0.10) 0%, rgba(236, 72, 153, 0.08) 100%);
  color: var(--foreground);
  padding: 12px 28px;
  font-size: 14px;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 12px;
  border-bottom: 1px solid var(--border);
  position: relative;
}
.announcement::before {
  content: "";
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 3px;
  background: linear-gradient(180deg, var(--accent), #ec4899);
}
.dark .announcement {
  background: linear-gradient(135deg, rgba(167, 139, 250, 0.12) 0%, rgba(236, 72, 153, 0.08) 100%);
  color: var(--foreground);
  border-bottom-color: var(--border);
}
.announcement.hidden { display: none; }
.announcement .icon { font-size: 18px; }
.announcement .text { flex: 1; white-space: pre-wrap; }
.announcement .btn-ghost { color: var(--accent); font-weight: 600; }
.announcement .btn-ghost:hover { background: var(--accent-soft); color: var(--accent); }

/* ============================================
   Toolbar
   ============================================ */
.toolbar {
  background: var(--header-bg);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--border);
  padding: 12px 28px;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  align-items: center;
}
.toolbar input,
.toolbar select {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 9px 14px;
  outline: none;
  color: var(--foreground);
  font-size: 14px;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.toolbar input { flex: 1; min-width: 220px; max-width: 360px; }
.toolbar input:focus,
.toolbar select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

/* ============================================
   Board layouts
   ============================================ */
.board { padding: 28px 28px 96px; }
.board:not(.board-sections):not(.board-landing) {
  column-count: 4;
  column-gap: 18px;
}
.board:not(.board-sections):not(.board-landing) > * { break-inside: avoid; margin-bottom: 18px; }
@media (max-width: 1200px) { .board:not(.board-sections):not(.board-landing) { column-count: 3; } }
@media (max-width: 840px)  { .board:not(.board-sections):not(.board-landing) { column-count: 2; padding: 20px; } }
@media (max-width: 540px)  { .board:not(.board-sections):not(.board-landing) { column-count: 1; } }

/* Landing variant — single-column flow, no masonry */
.board.board-landing {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  column-count: unset;
  padding: 8px 0 96px;
}

/* Padlet-style column sections */
.board-sections {
  display: flex;
  flex-direction: row;
  align-items: flex-start;
  gap: 18px;
  padding: 28px 28px 96px;
  overflow-x: auto;
  overflow-y: visible;
  column-count: unset !important;
  -webkit-overflow-scrolling: touch;
}
.section-column {
  flex: 0 0 320px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 14px;
  max-height: calc(100vh - 220px);
  overflow-y: auto;
  box-shadow: var(--shadow-card);
}
.section-header {
  background: var(--foreground);
  color: var(--background);
  padding: 10px 14px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 4px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.18);
}
.dark .section-header { background: var(--surface-2); color: var(--foreground); }
.section-title {
  margin: 0;
  font-size: 15px;
  font-weight: 700;
  flex: 1;
  min-width: 0;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  letter-spacing: -0.01em;
}
.section-actions { display: inline-flex; gap: 2px; }
.section-actions .btn-ghost {
  color: rgba(255, 255, 255, 0.7);
  padding: 4px 6px;
  font-size: 13px;
}
.section-actions .btn-ghost:hover {
  background: rgba(255, 255, 255, 0.15);
  color: white;
}
.dark .section-actions .btn-ghost { color: var(--muted); }
.dark .section-actions .btn-ghost:hover { background: var(--surface-3); color: var(--foreground); }

.section-add-post {
  background: transparent;
  border: 1px dashed var(--border-strong);
  color: var(--muted);
  padding: 8px 12px;
  border-radius: 8px;
  font-size: 13px;
  font-weight: 500;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.section-add-post:hover {
  background: var(--accent-soft);
  color: var(--accent);
  border-color: var(--accent);
}
.section-posts { display: flex; flex-direction: column; gap: 12px; }
.section-empty {
  font-size: 13px;
  color: var(--muted);
  text-align: center;
  padding: 16px 0;
}
.section-add-btn {
  flex: 0 0 240px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 28px;
  background: transparent;
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius-lg);
  color: var(--muted);
  font-size: 14px;
  font-weight: 600;
  min-height: 120px;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.section-add-btn:hover {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
}
.section-add-icon { font-size: 28px; line-height: 1; }

/* Drag states */
.post.draggable { cursor: grab; }
.post.dragging { opacity: 0.4; cursor: grabbing; }
.section-posts.post-drop-target {
  outline: 2px dashed var(--accent);
  outline-offset: 4px;
  background: var(--accent-soft);
  border-radius: 10px;
  min-height: 60px;
}
.section-header.dragging { opacity: 0.5; }
.section-column.section-drop-target {
  outline: 2px dashed var(--accent);
  outline-offset: 4px;
}

/* Sub-sections */
.sub-section {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  margin-top: 10px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.sub-section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 6px;
  padding: 0 2px 4px;
  border-bottom: 1px dashed var(--border);
}
.sub-section-title {
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  flex: 1;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.sub-section-actions { display: inline-flex; gap: 2px; }
.sub-section-actions .btn-ghost { padding: 2px 5px; font-size: 12px; }
.sub-add-post { font-size: 12px; padding: 4px 8px; }
.sub-section .section-posts { gap: 8px; }
.sub-section .post { padding: 12px; }
.sub-section .post .post-title { font-size: 14px; }
.sub-section .post .post-body { font-size: 13px; }

/* ============================================
   Post card
   ============================================ */
.post {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px;
  box-shadow: var(--shadow-card);
  cursor: pointer;
  transition: transform 0.18s ease, box-shadow 0.18s ease, border-color 0.18s ease;
  position: relative;
  display: inline-block;
  width: 100%;
  animation: pop-in 0.22s ease-out;
}
.post:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  border-color: var(--border-strong);
}
.post.pinned { border: 2px solid var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.pin-icon {
  position: absolute;
  top: -8px; right: 14px;
  background: var(--accent);
  color: white;
  font-size: 11px;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 999px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}
.post .post-image {
  width: 100%;
  border-radius: 10px;
  display: block;
  margin-bottom: 10px;
  max-height: 360px;
  object-fit: cover;
}
.post .post-image + .post-image { margin-top: 8px; }

.media-embed {
  position: relative;
  width: 100%;
  padding-top: 56.25%;
  margin-bottom: 10px;
  border-radius: 10px;
  overflow: hidden;
  background: #000;
}
.media-embed iframe {
  position: absolute;
  top: 0; left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.yt-thumb {
  position: relative;
  width: 100%;
  border-radius: 10px;
  overflow: hidden;
  margin-bottom: 10px;
  background: #000;
  cursor: pointer;
  aspect-ratio: 16 / 9;
}
.yt-thumb img { width: 100%; height: 100%; display: block; object-fit: cover; }
.yt-play {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 56px;
  height: 56px;
  background: rgba(0, 0, 0, 0.75);
  border-radius: 50%;
  color: white;
  font-size: 22px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  padding-left: 4px;
  transition: background 0.15s, transform 0.15s;
}
.yt-thumb:hover .yt-play {
  background: rgba(255, 0, 0, 0.85);
  transform: translate(-50%, -50%) scale(1.06);
}

/* Link preview card */
.link-preview {
  display: block;
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
  margin-bottom: 10px;
  text-decoration: none;
  color: var(--foreground);
  background: var(--surface);
  transition: background 0.15s;
}
.link-preview:hover { background: var(--surface-2); text-decoration: none; }
.link-preview-image { width: 100%; max-height: 200px; object-fit: cover; display: block; }
.link-preview-icon {
  background: linear-gradient(135deg, var(--accent-soft) 0%, rgba(236, 72, 153, 0.10) 100%);
  padding: 22px 12px;
  font-size: 32px;
  text-align: center;
  border-bottom: 1px solid var(--border);
  line-height: 1;
}
.link-preview-body { padding: 10px 12px; }
.link-preview-title {
  font-size: 14px;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 4px;
  word-break: break-word;
}
.link-preview-desc {
  font-size: 12px;
  color: var(--muted);
  line-height: 1.4;
  margin-bottom: 4px;
  white-space: pre-wrap;
  word-break: break-word;
}
.link-preview-host {
  font-size: 11px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 600;
}
.link-preview-wrap { margin-top: 8px; }
.link-preview-wrap:empty { margin-top: 0; }

/* PDF stack */
.pdf-pages {
  display: flex;
  flex-direction: column;
  gap: 4px;
  margin-bottom: 14px;
  background: var(--surface-2);
  padding: 10px;
  border-radius: 10px;
  max-height: 70vh;
  overflow-y: auto;
}
.pdf-page {
  width: 100%;
  display: block;
  border-radius: 4px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.15);
  background: #fff;
}
.pdf-page-label {
  text-align: center;
  font-size: 11px;
  color: var(--muted);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  margin-top: 2px;
  margin-bottom: 6px;
  font-weight: 600;
}
.pdf-note { margin-top: 8px; font-size: 12px; color: var(--muted); font-style: italic; }

.post .post-title {
  font-size: 16px;
  font-weight: 700;
  margin: 0 0 6px;
  line-height: 1.3;
  letter-spacing: -0.01em;
  word-break: break-word;
}
.post .post-body {
  font-size: 14px;
  line-height: 1.55;
  color: var(--foreground-soft);
  margin: 0 0 10px;
  white-space: pre-wrap;
  word-break: break-word;
}
.post .post-link {
  font-size: 13px;
  color: var(--accent);
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin-bottom: 10px;
  word-break: break-all;
}
.post .post-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-top: 12px;
  padding-top: 10px;
  border-top: 1px solid var(--border);
  font-size: 12px;
  color: var(--muted);
}
.post .author-row { display: flex; align-items: center; gap: 6px; }
.like-btn {
  background: none;
  border: none;
  color: var(--muted);
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 13px;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: 999px;
  transition: background 0.15s, color 0.15s;
}
.like-btn:hover { background: var(--surface-2); }
.like-btn.liked { color: var(--danger); }
.like-btn .heart { font-size: 16px; }

.category-chip {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: 11px;
  font-weight: 700;
  color: #1e293b;
  margin-bottom: 8px;
  letter-spacing: 0.02em;
}

/* ============================================
   FAB
   ============================================ */
.fab {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 60px; height: 60px;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--accent), #ec4899);
  color: white;
  border: none;
  font-size: 28px;
  box-shadow: 0 6px 20px rgba(124, 58, 237, 0.40), 0 12px 32px rgba(0, 0, 0, 0.14);
  z-index: 30;
  transition: transform 0.18s, box-shadow 0.18s;
}
.fab:hover { transform: scale(1.06) rotate(90deg); box-shadow: 0 8px 26px rgba(124, 58, 237, 0.50), 0 16px 36px rgba(0, 0, 0, 0.20); }

/* ============================================
   Modal
   ============================================ */
.modal-overlay {
  position: fixed; inset: 0;
  background: rgba(15, 23, 42, 0.55);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  display: flex; align-items: center; justify-content: center;
  z-index: 50;
  padding: 20px;
  animation: fade-in 0.18s ease-out;
}
.modal {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  width: 100%;
  max-width: 540px;
  padding: 28px;
  max-height: 90vh;
  overflow-y: auto;
  animation: pop-in 0.22s ease-out;
  box-shadow: var(--shadow-lg);
  position: relative;
}
.modal-close-btn {
  position: absolute;
  top: 14px;
  right: 14px;
  background: transparent;
  border: none;
  font-size: 22px;
  line-height: 1;
  color: var(--muted);
  width: 32px;
  height: 32px;
  border-radius: 8px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
}
.modal-close-btn:hover { background: var(--surface-2); color: var(--foreground); }
.modal.wide { max-width: 720px; }
.modal h2 { margin: 0 0 18px; font-size: 22px; font-weight: 700; letter-spacing: -0.02em; }
.modal label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 6px;
  margin-top: 14px;
  color: var(--foreground-soft);
}
.modal label:first-child, .modal h2 + label { margin-top: 0; }
.modal input[type=text],
.modal input[type=url],
.modal input[type=email],
.modal textarea,
.modal select {
  width: 100%;
  padding: 10px 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--foreground);
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.modal textarea { min-height: 90px; resize: vertical; line-height: 1.5; }
.modal input:focus,
.modal textarea:focus,
.modal select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.modal-actions { display: flex; justify-content: flex-end; gap: 8px; margin-top: 20px; }
.modal-actions.between { justify-content: space-between; }

.image-preview { margin-top: 10px; }
.image-preview img { max-width: 100%; max-height: 220px; border-radius: 10px; }

.image-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
  gap: 8px;
  margin: 8px 0 4px;
}
.image-list:empty { display: none; }
.image-item {
  position: relative;
  border-radius: 8px;
  overflow: hidden;
  aspect-ratio: 1;
  background: var(--surface-2);
}
.image-item img { width: 100%; height: 100%; object-fit: cover; display: block; }
.image-item-remove {
  position: absolute;
  top: 4px; right: 4px;
  background: rgba(0, 0, 0, 0.7);
  color: white;
  border: none;
  width: 22px; height: 22px;
  font-size: 16px;
  line-height: 1;
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
}
.image-item-remove:hover { background: var(--danger); }

.pdf-status { margin: 8px 0 4px; }
.pdf-status:empty { margin: 0; }
.pdf-thumb {
  max-height: 180px;
  border-radius: 6px;
  display: block;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.15);
}

.detail-image + .detail-image { margin-top: 14px; }
.detail-image { width: 100%; max-height: 400px; object-fit: cover; border-radius: 12px; margin-bottom: 14px; }
.detail-title { font-size: 24px; font-weight: 700; margin: 0 0 6px; word-break: break-word; letter-spacing: -0.02em; }
.detail-meta { display: flex; align-items: center; gap: 10px; color: var(--muted); font-size: 13px; margin-bottom: 14px; flex-wrap: wrap; }
.detail-body { font-size: 15px; line-height: 1.65; white-space: pre-wrap; margin: 0 0 14px; word-break: break-word; }
.detail-link { display: inline-block; margin-bottom: 14px; word-break: break-all; }

.detail-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  padding: 14px 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  margin-bottom: 14px;
}

/* ============================================
   Composer (New / Edit post) — Padlet-style
   ============================================ */
.modal.composer-modal { padding: 0; max-width: 600px; }
.composer { display: flex; flex-direction: column; }

.composer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 18px;
  border-bottom: 1px solid var(--border);
}
.composer-close-btn {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--foreground);
  width: 36px;
  height: 36px;
  border-radius: 999px;
  font-size: 22px;
  line-height: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}
.composer-close-btn:hover { background: var(--surface-3); border-color: var(--border-strong); }

.composer-submit {
  padding: 8px 22px;
  font-size: 14px;
  border-radius: 999px;
}

.composer-subject {
  width: 100%;
  border: none;
  outline: none;
  background: transparent;
  color: var(--foreground);
  padding: 18px 24px 6px;
  font-size: 28px;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
}
.composer-subject::placeholder { color: var(--muted); font-weight: 700; }

.composer-tiles-wrap {
  padding: 0 24px;
  margin-bottom: 4px;
}
.composer-tiles {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0;
  border: 1px dashed var(--border-strong);
  border-radius: 14px;
  overflow: hidden;
  background:
    repeating-linear-gradient(
      135deg,
      transparent 0 10px,
      var(--surface-2) 10px 11px
    ),
    var(--surface);
}
.composer-tile {
  background: transparent;
  border: none;
  border-right: 1px dashed var(--border);
  padding: 22px 8px 18px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  color: var(--foreground);
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}
.composer-tile:last-child { border-right: none; }
.composer-tile:hover { background: var(--accent-soft); color: var(--accent); }
.composer-tile-icon { font-size: 22px; line-height: 1; filter: grayscale(0.1); }
.composer-tile-label {
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  letter-spacing: 0.02em;
}
.composer-tile:hover .composer-tile-label { color: var(--accent); }
.composer-tiles-hint {
  text-align: center;
  font-size: 12px;
  color: var(--muted);
  padding: 8px 0 4px;
}

.composer-body {
  width: 100%;
  border: none;
  outline: none;
  background: transparent;
  color: var(--foreground);
  padding: 14px 24px 18px;
  font-size: 16px;
  line-height: 1.55;
  resize: vertical;
  min-height: 88px;
  font-family: inherit;
}
.composer-body::placeholder { color: var(--muted); }

.composer-attachments {
  padding: 0 24px 18px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.composer-attachments .image-list:empty,
.composer-attachments .pdf-status:empty { margin: 0; }

.composer-links {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin: 6px 0;
}
.composer-links[hidden] { display: none; }
.composer-link-row {
  display: flex;
  align-items: center;
  gap: 8px;
}
.composer-link-input {
  flex: 1;
  padding: 10px 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--foreground);
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.composer-link-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.composer-link-remove {
  width: 32px;
  height: 32px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--muted);
  border-radius: 8px;
  font-size: 18px;
  line-height: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  flex-shrink: 0;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.composer-link-remove:hover {
  background: rgba(239, 68, 68, 0.10);
  color: var(--danger);
  border-color: var(--danger);
}
.composer-add-more {
  align-self: flex-start;
  background: transparent;
  border: 1px dashed var(--border-strong);
  color: var(--accent);
  padding: 6px 12px;
  border-radius: 8px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  margin-top: 2px;
  transition: background 0.15s, border-color 0.15s;
}
.composer-add-more:hover {
  background: var(--accent-soft);
  border-color: var(--accent);
}

.composer-section-row {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 24px;
  border-top: 1px solid var(--border);
  margin-top: 12px;
}
.composer-section-label {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}
.composer-section-row select {
  flex: 1;
  padding: 8px 12px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--foreground);
  outline: none;
}
.composer-section-row select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.composer .pdf-note {
  margin: 10px 24px 18px;
  padding: 10px 12px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 13px;
}

/* ============================================
   Comments
   ============================================ */
.comment-thread { display: flex; flex-direction: column; gap: 10px; margin-bottom: 14px; }
.comment {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 12px;
  position: relative;
}
.comment .head { font-size: 12px; color: var(--muted); margin-bottom: 4px; display: flex; gap: 6px; }
.comment .head strong { color: var(--foreground); font-weight: 600; }
.comment .text { font-size: 14px; line-height: 1.55; white-space: pre-wrap; word-break: break-word; }
.comment .delete-btn {
  position: absolute;
  top: 6px; right: 6px;
  background: none;
  border: none;
  color: var(--muted);
  font-size: 14px;
  padding: 2px 6px;
  border-radius: 6px;
}
.comment .delete-btn:hover { background: var(--background); color: var(--danger); }
.comment-empty { color: var(--muted); font-size: 13px; padding: 8px 0; }

.comment-form { display: flex; gap: 8px; align-items: flex-end; }
.comment-form textarea {
  flex: 1;
  min-height: 40px;
  max-height: 120px;
  padding: 9px 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--foreground);
  outline: none;
  resize: vertical;
}
.comment-form textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

/* Sign-in modal */
.signin-buttons { display: flex; flex-direction: column; gap: 10px; margin-top: 16px; }
.signin-buttons .btn { padding: 12px 16px; font-size: 15px; }
.signin-divider { text-align: center; color: var(--muted); font-size: 12px; margin: 14px 0; }
.signin-google {
  background: #fff;
  color: #1f2937;
  border: 1px solid var(--border-strong);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  box-shadow: var(--shadow-sm);
}
.signin-google:hover { background: #f9fafb; box-shadow: var(--shadow); }
.dark .signin-google { background: #fff; color: #1f2937; }

/* ============================================
   Toast
   ============================================ */
#toast-root {
  position: fixed;
  top: 20px;
  right: 20px;
  z-index: 100;
  display: flex;
  flex-direction: column;
  gap: 8px;
  pointer-events: none;
}
.toast {
  background: var(--surface);
  color: var(--foreground);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px 16px;
  font-size: 14px;
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transform: translateX(20px);
  transition: opacity 0.3s, transform 0.3s;
  pointer-events: auto;
  border-left: 3px solid var(--muted);
  max-width: 360px;
}
.toast.show { opacity: 1; transform: translateX(0); }
.toast-success { border-left-color: var(--success); }
.toast-error { border-left-color: var(--danger); }
.toast-info { border-left-color: var(--accent); }

/* ============================================
   Footer
   ============================================ */
.app-footer {
  text-align: center;
  padding: 24px 28px 100px;
  font-size: 13px;
  color: var(--muted);
  border-top: 1px solid var(--border);
  background: var(--surface);
}
.app-footer a { color: var(--accent); font-weight: 600; }

/* ============================================
   Empty state
   ============================================ */
.empty-state {
  text-align: center;
  padding: 80px 20px;
  color: var(--muted);
}
.empty-state h2 { color: var(--foreground); margin: 0 0 8px; font-weight: 700; letter-spacing: -0.01em; }

/* ============================================
   Landing page (Create / Join classroom)
   ============================================ */
.landing {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 20px;
  max-width: 920px;
  margin: 24px auto 40px;
  padding: 0 20px;
  column-span: all;
}
.landing-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-card);
  transition: box-shadow 0.2s, transform 0.2s, border-color 0.2s;
}
.landing-card:hover {
  box-shadow: var(--shadow);
  border-color: var(--border-strong);
}
.landing-card h2 {
  margin: 0 0 8px;
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.02em;
}
.landing-hint { color: var(--muted); font-size: 14px; margin: 0 0 20px; line-height: 1.55; }
.landing-card label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 6px;
  margin-top: 14px;
  color: var(--foreground-soft);
}
.landing-card input {
  width: 100%;
  padding: 10px 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--foreground);
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.landing-card input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.landing-actions {
  display: flex;
  gap: 8px;
  margin-top: 20px;
  flex-wrap: wrap;
}
.landing-actions .btn { flex: 1; min-width: 140px; padding: 11px 18px; font-size: 14px; }

/* Room code in title */
.room-code {
  font-size: 13px;
  color: var(--muted);
  font-weight: 500;
  letter-spacing: 0.06em;
  font-family: ui-monospace, "SF Mono", SFMono-Regular, Menlo, monospace;
  margin-left: 8px;
  padding: 2px 8px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 6px;
}

/* Sign-in panel — top of landing */
.landing-signin {
  max-width: 920px;
  margin: 32px auto 0;
  padding: 22px 24px;
  display: flex;
  align-items: center;
  gap: 18px;
  background: linear-gradient(135deg, var(--surface) 0%, var(--surface-2) 100%);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  column-span: all;
  flex-wrap: wrap;
  position: relative;
  overflow: hidden;
}
.landing-signin::before {
  content: "";
  position: absolute;
  top: -40px;
  right: -40px;
  width: 180px;
  height: 180px;
  background: radial-gradient(circle, var(--accent-soft), transparent 70%);
  pointer-events: none;
}
.landing-signin-info { flex: 1; min-width: 220px; position: relative; }
.landing-signin-info strong {
  display: block;
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 6px;
  letter-spacing: -0.01em;
  color: var(--foreground);
}
.landing-signin-hint {
  font-size: 13px;
  color: var(--muted);
  line-height: 1.5;
}
.landing-signin .btn { position: relative; }

/* Recent rooms */
.landing-recent {
  max-width: 920px;
  margin: 24px auto 0;
  padding: 0 20px;
  column-span: all;
}
.landing-recent h2 {
  font-size: 14px;
  font-weight: 700;
  margin: 0 0 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}
.recent-list {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  overflow: hidden;
}
.recent-row {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 18px;
  border-bottom: 1px solid var(--border);
  transition: background 0.15s;
}
.recent-row:last-child { border-bottom: none; }
.recent-row:hover { background: var(--surface-2); }
.recent-info { flex: 1; min-width: 0; }
.recent-title {
  font-weight: 600;
  font-size: 15px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  color: var(--foreground);
  letter-spacing: -0.01em;
}
.recent-code {
  font-size: 12px;
  color: var(--muted);
  font-family: ui-monospace, "SF Mono", SFMono-Regular, Menlo, monospace;
  letter-spacing: 0.06em;
  margin-top: 2px;
}
.recent-remove {
  font-size: 18px;
  line-height: 1;
  padding: 4px 10px;
}
.recent-delete {
  font-size: 16px;
  padding: 8px 10px;
  border-radius: 8px;
  color: var(--muted);
  transition: background 0.15s, color 0.15s;
}
.recent-delete:hover { background: rgba(239, 68, 68, 0.10); color: var(--danger); }

/* ============================================
   Animations
   ============================================ */
@keyframes pop-in {
  0% { opacity: 0; transform: scale(0.97) translateY(4px); }
  100% { opacity: 1; transform: scale(1) translateY(0); }
}
@keyframes fade-in {
  0% { opacity: 0; }
  100% { opacity: 1; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}