/* ============================================================
   AI WORKBENCH — Apple-Standard Design System
   SF Pro · Glassmorphism · True Black · Spring Animations
   ============================================================ */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  /* Apple Dark Palette */
  --bg-base:        #000000;
  --bg-primary:     #0d0d0f;
  --bg-secondary:   #1c1c1e;
  --bg-tertiary:    #2c2c2e;
  --bg-elevated:    #3a3a3c;
  --bg-glass:       rgba(28, 28, 30, 0.72);
  --bg-glass-hover: rgba(44, 44, 46, 0.80);

  /* Apple Separators */
  --sep:            rgba(255, 255, 255, 0.08);
  --sep-strong:     rgba(255, 255, 255, 0.14);

  /* Apple Labels */
  --label:          rgba(255, 255, 255, 0.95);
  --label-2:        rgba(255, 255, 255, 0.60);
  --label-3:        rgba(255, 255, 255, 0.35);
  --label-4:        rgba(255, 255, 255, 0.18);

  /* Apple System Colours */
  --blue:           #007AFF;
  --blue-light:     #409CFF;
  --blue-dim:       rgba(0, 122, 255, 0.18);
  --green:          #30D158;
  --green-dim:      rgba(48, 209, 88, 0.16);
  --purple:         #BF5AF2;
  --purple-dim:     rgba(191, 90, 242, 0.16);
  --orange:         #FF9F0A;
  --orange-dim:     rgba(255, 159, 10, 0.16);
  --pink:           #FF375F;
  --pink-dim:       rgba(255, 55, 95, 0.16);
  --teal:           #5AC8FA;
  --teal-dim:       rgba(90, 200, 250, 0.16);
  --yellow:         #FFD60A;

  /* Layout */
  --header-h:       52px;
  --sidebar-w:      264px;
  --radius-sm:      8px;
  --radius:         12px;
  --radius-lg:      16px;
  --radius-xl:      20px;

  /* Shadows */
  --shadow-sm:      0 1px 3px rgba(0,0,0,0.4), 0 1px 2px rgba(0,0,0,0.3);
  --shadow:         0 4px 16px rgba(0,0,0,0.5), 0 1px 4px rgba(0,0,0,0.4);
  --shadow-lg:      0 12px 40px rgba(0,0,0,0.6), 0 4px 12px rgba(0,0,0,0.4);
  --shadow-blue:    0 0 0 3px rgba(0, 122, 255, 0.30);

  /* Transitions */
  --spring:         cubic-bezier(0.34, 1.56, 0.64, 1);
  --ease:           cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

html, body {
  height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'SF Pro Text',
               'Helvetica Neue', sans-serif;
  background: var(--bg-base);
  color: var(--label);
  font-size: 14px;
  line-height: 1.5;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Push content below fixed headers on all tool pages */
body:has(.aiw-header),
body:has(.tool-header) {
  padding-top: var(--header-h);
}

/* ── SCROLLBAR ──────────────────────────────────────────── */
::-webkit-scrollbar { width: 5px; height: 5px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.12); border-radius: 10px; }
::-webkit-scrollbar-thumb:hover { background: rgba(255,255,255,0.22); }

/* ── HEADER ─────────────────────────────────────────────── */
.aiw-header {
  display: flex;
  align-items: center;
  gap: 12px;
  height: var(--header-h);
  background: rgba(10, 10, 12, 0.85);
  backdrop-filter: blur(24px) saturate(1.8);
  -webkit-backdrop-filter: blur(24px) saturate(1.8);
  border-bottom: 1px solid var(--sep);
  padding: 0 20px;
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 200;
}

.aiw-header .logo {
  display: flex;
  align-items: center;
  gap: 9px;
  font-weight: 700;
  font-size: 15px;
  color: var(--label);
  text-decoration: none;
  letter-spacing: -0.3px;
}
.aiw-header .logo-icon {
  width: 30px; height: 30px;
  background: linear-gradient(135deg, var(--blue) 0%, var(--purple) 100%);
  border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  font-size: 14px; color: #fff;
  box-shadow: 0 2px 8px rgba(0,122,255,0.4);
}
.aiw-header .title {
  font-size: 13px;
  color: var(--label-3);
  font-weight: 400;
  letter-spacing: 0;
}
.aiw-header .title span { color: var(--blue-light); font-weight: 600; }

.header-spacer { flex: 1; }

.aiw-header .class-badge {
  background: var(--blue-dim);
  color: var(--blue-light);
  border: 1px solid rgba(0, 122, 255, 0.3);
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: -0.1px;
}

.aiw-header .user-info {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--label-2);
}
.aiw-header .user-avatar {
  width: 30px; height: 30px;
  background: linear-gradient(135deg, var(--purple), var(--blue));
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-size: 12px; color: #fff; font-weight: 700;
  box-shadow: 0 2px 6px rgba(191,90,242,0.35);
}
.aiw-header .btn-logout {
  background: rgba(255,255,255,0.06);
  border: 1px solid var(--sep-strong);
  color: var(--label-2);
  padding: 5px 12px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 12px;
  font-weight: 500;
  transition: all 0.18s var(--ease);
  font-family: inherit;
}
.aiw-header .btn-logout:hover {
  background: rgba(255,255,255,0.10);
  color: var(--label);
}

/* ── LAYOUT ─────────────────────────────────────────────── */
.aiw-layout {
  display: flex;
  height: 100%;
}

/* ── SIDEBAR ────────────────────────────────────────────── */
.aiw-sidebar {
  width: var(--sidebar-w);
  min-width: var(--sidebar-w);
  background: rgba(18, 18, 20, 0.95);
  border-right: 1px solid var(--sep);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.sidebar-top { padding: 14px 12px; border-bottom: 1px solid var(--sep); }

.class-selector {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 5px;
}
.class-btn {
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--sep);
  color: var(--label-3);
  padding: 7px 4px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 13px;
  font-weight: 600;
  text-align: center;
  transition: all 0.22s var(--spring);
  font-family: inherit;
  letter-spacing: -0.2px;
}
.class-btn:hover {
  background: rgba(0,122,255,0.10);
  color: var(--blue-light);
  border-color: rgba(0,122,255,0.25);
  transform: scale(1.04);
}
.class-btn.active {
  background: var(--blue);
  border-color: var(--blue);
  color: #fff;
  box-shadow: 0 2px 10px rgba(0,122,255,0.45);
  transform: scale(1.04);
}

.sidebar-search { padding: 10px 12px; border-bottom: 1px solid var(--sep); }
.sidebar-search input {
  width: 100%;
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--sep-strong);
  color: var(--label);
  padding: 7px 10px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  outline: none;
  font-family: inherit;
  transition: border-color 0.18s;
}
.sidebar-search input::placeholder { color: var(--label-3); }
.sidebar-search input:focus {
  border-color: var(--blue);
  box-shadow: var(--shadow-blue);
  background: rgba(255,255,255,0.07);
}

.sidebar-nav { flex: 1; overflow-y: auto; padding: 8px 0; }

.unit-group { margin-bottom: 2px; }
.unit-header {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 7px 14px;
  cursor: pointer;
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--label-3);
  user-select: none;
  transition: background 0.15s;
  border-radius: 6px;
  margin: 0 6px;
}
.unit-header:hover { background: rgba(255,255,255,0.04); color: var(--label-2); }
.unit-header .unit-icon { font-size: 11px; }
.unit-header .unit-chevron { margin-left: auto; transition: transform 0.22s var(--ease); font-size: 9px; }
.unit-header.open .unit-chevron { transform: rotate(90deg); }

.chapter-list { display: none; padding: 2px 6px; }
.chapter-list.visible { display: block; }
.chapter-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 7px 10px 7px 22px;
  cursor: pointer;
  font-size: 12.5px;
  color: var(--label-2);
  transition: all 0.18s var(--ease);
  border-radius: var(--radius-sm);
  margin-bottom: 1px;
}
.chapter-item:hover { background: rgba(255,255,255,0.05); color: var(--label); }
.chapter-item.active {
  color: var(--blue-light);
  background: rgba(0, 122, 255, 0.12);
  font-weight: 600;
}
.chapter-item .ch-progress { margin-left: auto; font-size: 10px; color: var(--green); font-weight: 600; }

.sidebar-bottom {
  padding: 12px 14px;
  border-top: 1px solid var(--sep);
}
.streak-badge {
  display: flex;
  align-items: center;
  gap: 7px;
  font-size: 12px;
  color: var(--orange);
  font-weight: 600;
  background: var(--orange-dim);
  padding: 6px 10px;
  border-radius: var(--radius-sm);
}

/* ── MAIN CONTENT ───────────────────────────────────────── */
.aiw-main {
  flex: 1;
  overflow-y: auto;
  background: var(--bg-primary);
}

/* ── WELCOME VIEW ───────────────────────────────────────── */
.welcome-view { padding: 36px 32px; }

.welcome-hero {
  margin-bottom: 32px;
}
.welcome-hero h1 {
  font-size: 28px;
  font-weight: 700;
  color: var(--label);
  letter-spacing: -0.6px;
  line-height: 1.2;
  margin-bottom: 6px;
}
.welcome-hero h1 .gradient-text {
  background: linear-gradient(90deg, var(--blue-light), var(--purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.welcome-hero .subtitle {
  color: var(--label-2);
  font-size: 14px;
  font-weight: 400;
}
.welcome-hero .subtitle span { color: var(--blue-light); font-weight: 500; }

/* Section heading */
.section-heading {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--label-3);
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  gap: 7px;
}
.section-heading::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--sep);
}

/* ── TOOL CARDS GRID ────────────────────────────────────── */
.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 14px;
  margin-bottom: 36px;
}

.tool-card {
  background: var(--bg-secondary);
  border: 1px solid var(--sep);
  border-radius: var(--radius-lg);
  padding: 20px;
  cursor: pointer;
  transition: all 0.28s var(--spring);
  text-decoration: none;
  display: block;
  position: relative;
  overflow: hidden;
}
.tool-card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--card-color-dim, rgba(0,122,255,0.04)) 0%, transparent 60%);
  opacity: 0;
  transition: opacity 0.25s;
}
.tool-card:hover {
  border-color: var(--card-color, var(--blue));
  background: var(--bg-tertiary);
  transform: translateY(-3px) scale(1.01);
  box-shadow: var(--shadow-lg), 0 0 0 1px var(--card-color, var(--blue));
}
.tool-card:hover::before { opacity: 1; }

.tool-card .tool-icon {
  width: 46px; height: 46px;
  background: var(--card-color-dim, var(--blue-dim));
  border-radius: var(--radius);
  display: flex; align-items: center; justify-content: center;
  font-size: 20px;
  margin-bottom: 14px;
  color: var(--card-color, var(--blue));
  transition: transform 0.28s var(--spring);
}
.tool-card:hover .tool-icon { transform: scale(1.1) rotate(-4deg); }

.tool-card .tool-name {
  font-size: 15px;
  font-weight: 700;
  color: var(--label);
  margin-bottom: 5px;
  letter-spacing: -0.2px;
}
.tool-card .tool-desc {
  font-size: 12px;
  color: var(--label-2);
  line-height: 1.5;
  margin-bottom: 12px;
}
.tool-card .tool-tags { display: flex; gap: 5px; flex-wrap: wrap; }
.tool-card .tag {
  background: rgba(255,255,255,0.06);
  color: var(--label-3);
  padding: 3px 8px;
  border-radius: 20px;
  font-size: 10px;
  font-weight: 500;
  border: 1px solid var(--sep);
}

/* ── PROGRESS STATS ─────────────────────────────────────── */
.progress-section { margin-top: 4px; }
.progress-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}
.progress-stat {
  background: var(--bg-secondary);
  border: 1px solid var(--sep);
  border-radius: var(--radius-lg);
  padding: 18px 16px;
  text-align: center;
  transition: all 0.22s var(--spring);
}
.progress-stat:hover { background: var(--bg-tertiary); transform: translateY(-2px); box-shadow: var(--shadow); }
.progress-stat .stat-val {
  font-size: 28px;
  font-weight: 700;
  color: var(--blue-light);
  letter-spacing: -1px;
  line-height: 1;
  margin-bottom: 4px;
}
.progress-stat .stat-label { font-size: 11px; color: var(--label-3); font-weight: 500; }

/* ── CHAPTER VIEW ───────────────────────────────────────── */
.chapter-view { padding: 28px 32px; display: none; }
.chapter-view.visible { display: block; }

.chapter-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}
.chapter-header .back-btn {
  background: rgba(255,255,255,0.06);
  border: 1px solid var(--sep-strong);
  color: var(--label-2);
  width: 32px; height: 32px;
  border-radius: 10px;
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  font-size: 13px;
  transition: all 0.18s var(--spring);
  font-family: inherit;
}
.chapter-header .back-btn:hover {
  background: rgba(255,255,255,0.10);
  color: var(--label);
  transform: scale(1.08);
}
.chapter-header h2 {
  font-size: 22px;
  font-weight: 700;
  color: var(--label);
  letter-spacing: -0.4px;
}
.diff-badge {
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 11px;
  font-weight: 600;
}
.diff-easy   { background: var(--green-dim); color: var(--green); }
.diff-medium { background: var(--orange-dim); color: var(--orange); }
.diff-hard   { background: var(--pink-dim); color: var(--pink); }

.topics-list { margin-bottom: 28px; }
.topic-pill {
  display: inline-flex;
  align-items: center;
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--sep);
  color: var(--label-2);
  padding: 5px 12px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 500;
  margin: 0 5px 7px 0;
  transition: all 0.18s;
}
.topic-pill:hover { background: var(--blue-dim); color: var(--blue-light); border-color: rgba(0,122,255,0.3); }

.chapter-tool-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 12px;
}
.chapter-tool-card {
  background: var(--bg-secondary);
  border: 1px solid var(--sep);
  border-radius: var(--radius-lg);
  padding: 16px;
  cursor: pointer;
  transition: all 0.25s var(--spring);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 12px;
}
.chapter-tool-card:hover {
  border-color: var(--card-color, var(--blue));
  background: var(--bg-tertiary);
  transform: translateY(-2px) scale(1.02);
  box-shadow: var(--shadow);
}
.chapter-tool-card .ctool-icon {
  font-size: 22px;
  color: var(--card-color, var(--blue));
  width: 36px; height: 36px;
  display: flex; align-items: center; justify-content: center;
  background: var(--card-color-dim, var(--blue-dim));
  border-radius: var(--radius-sm);
  flex-shrink: 0;
  transition: transform 0.22s var(--spring);
}
.chapter-tool-card:hover .ctool-icon { transform: scale(1.15) rotate(-5deg); }
.chapter-tool-card .ctool-name { font-size: 13px; font-weight: 600; color: var(--label); letter-spacing: -0.1px; }
.chapter-tool-card .ctool-sub  { font-size: 11px; color: var(--label-3); margin-top: 1px; }

/* ── SPINNER ────────────────────────────────────────────── */
.spinner {
  display: inline-block;
  width: 16px; height: 16px;
  border: 2px solid rgba(255,255,255,0.12);
  border-top-color: var(--blue);
  border-radius: 50%;
  animation: spin 0.65s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── TOOL PAGES SHARED ──────────────────────────────────── */
.tool-page {
  display: flex;
  flex-direction: column;
  height: 100vh;
  background: var(--bg-primary);
  color: var(--label);
}
.tool-header {
  display: flex;
  align-items: center;
  gap: 12px;
  height: var(--header-h);
  background: rgba(10, 10, 12, 0.88);
  backdrop-filter: blur(20px) saturate(1.6);
  -webkit-backdrop-filter: blur(20px) saturate(1.6);
  border-bottom: 1px solid var(--sep);
  padding: 0 20px;
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 200;
  flex-shrink: 0;
}
.tool-header .back-link,
.tool-header .back-btn {
  background: rgba(255,255,255,0.06);
  border: 1px solid var(--sep-strong);
  color: var(--label-2);
  padding: 5px 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 12px;
  font-weight: 500;
  text-decoration: none;
  display: flex; align-items: center; gap: 5px;
  transition: all 0.18s var(--ease);
  font-family: inherit;
  white-space: nowrap;
}
.tool-header .back-link:hover,
.tool-header .back-btn:hover { background: rgba(255,255,255,0.10); color: var(--label); }
.tool-header h1,
.tool-header .tool-header-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--label);
  letter-spacing: -0.3px;
  display: flex;
  align-items: center;
  gap: 7px;
}
.tool-header .tool-icon {
  font-size: 18px;
}
.tool-header .tool-badge {
  background: rgba(255,255,255,0.06);
  border: 1px solid var(--sep);
  color: var(--label-3);
  padding: 3px 9px;
  border-radius: 20px;
  font-size: 11px;
  font-weight: 500;
}
.tool-body { flex: 1; overflow: hidden; display: flex; }

/* ── BUTTONS ────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  font-size: 13px;
  font-weight: 600;
  transition: all 0.2s var(--spring);
  font-family: inherit;
  letter-spacing: -0.1px;
}
.btn-primary {
  background: var(--blue);
  color: #fff;
  box-shadow: 0 2px 8px rgba(0,122,255,0.35);
}
.btn-primary:hover { background: #1a8fff; transform: scale(1.03); box-shadow: 0 4px 14px rgba(0,122,255,0.45); }
.btn-secondary {
  background: rgba(255,255,255,0.07);
  color: var(--label);
  border: 1px solid var(--sep-strong);
}
.btn-secondary:hover { background: rgba(255,255,255,0.12); }
.btn-success {
  background: var(--green);
  color: #000;
  box-shadow: 0 2px 8px rgba(48,209,88,0.35);
}
.btn-success:hover { background: #45e070; transform: scale(1.03); }
.btn-danger  { background: var(--pink); color: #fff; }
.btn-danger:hover { background: #ff5474; }
.btn-sm { padding: 5px 11px; font-size: 12px; }
.btn:disabled { opacity: 0.35; cursor: not-allowed; transform: none !important; }

/* ── FORM CONTROLS ──────────────────────────────────────── */
select, input[type="text"], input[type="number"], textarea {
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--sep-strong);
  color: var(--label);
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  outline: none;
  font-family: inherit;
  transition: border-color 0.18s, box-shadow 0.18s;
}
select:focus, input:focus, textarea:focus {
  border-color: var(--blue);
  box-shadow: var(--shadow-blue);
  background: rgba(255,255,255,0.07);
}
select option { background: var(--bg-secondary); color: var(--label); }
label {
  font-size: 12px;
  color: var(--label-3);
  font-weight: 500;
  display: block;
  margin-bottom: 5px;
  letter-spacing: 0.1px;
}

/* ── PANELS ─────────────────────────────────────────────── */
.panel {
  background: var(--bg-secondary);
  border: 1px solid var(--sep);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.panel-header {
  padding: 10px 16px;
  border-bottom: 1px solid var(--sep);
  font-size: 11px;
  font-weight: 700;
  color: var(--label-3);
  text-transform: uppercase;
  letter-spacing: 0.7px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.panel-body { padding: 16px; }

/* ── TOAST ──────────────────────────────────────────────── */
.toast-container {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.toast {
  background: rgba(44, 44, 46, 0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--sep-strong);
  border-left: 3px solid var(--blue);
  color: var(--label);
  padding: 12px 16px;
  border-radius: var(--radius);
  font-size: 13px;
  font-weight: 500;
  min-width: 260px;
  max-width: 340px;
  box-shadow: var(--shadow-lg);
  animation: toastIn 0.3s var(--spring);
}
.toast.success { border-left-color: var(--green); }
.toast.error   { border-left-color: var(--pink); }
.toast.warning { border-left-color: var(--orange); }
@keyframes toastIn {
  from { transform: translateX(24px) scale(0.95); opacity: 0; }
  to   { transform: none; opacity: 1; }
}

/* ── PYODIDE / SKULPT STATUS ────────────────────────────── */
.pyodide-status { display: flex; align-items: center; gap: 6px; font-size: 11px; font-weight: 500; }
.py-dot { width: 7px; height: 7px; border-radius: 50%; background: var(--label-3); }
.py-dot.loading { background: var(--orange); animation: pulse 1.2s ease-in-out infinite; }
.py-dot.ready   { background: var(--green); box-shadow: 0 0 6px rgba(48,209,88,0.5); }
.py-dot.error   { background: var(--pink); }
@keyframes pulse { 0%,100% { opacity: 1; } 50% { opacity: 0.35; } }

/* ── HAMBURGER BUTTON ───────────────────────────────────── */
.hamburger-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 18px;
  cursor: pointer;
  padding: 6px 10px;
  border-radius: 6px;
  transition: background 0.15s;
}
.hamburger-btn:hover { background: var(--bg-tertiary); }

/* ── SIDEBAR OVERLAY (mobile) ───────────────────────────── */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.55);
  z-index: 199;
}
.sidebar-overlay.visible { display: block; }

/* ── RESPONSIVE ─────────────────────────────────────────── */
@media (max-width: 768px) {
  .hamburger-btn { display: flex; align-items: center; }
  .aiw-sidebar {
    display: flex;
    position: fixed;
    top: 0; left: 0; bottom: 0;
    z-index: 200;
    transform: translateX(-100%);
    transition: transform 0.25s var(--spring);
    width: 260px;
  }
  .aiw-sidebar.sidebar-open { transform: translateX(0); }
  .tools-grid { grid-template-columns: 1fr 1fr; }
  .progress-grid { grid-template-columns: repeat(3, 1fr); }
  .welcome-view, .chapter-view { padding: 20px 16px; }
  .welcome-hero h1 { font-size: 22px; }

  /* Header — shrink on mobile */
  .aiw-header { padding: 0 12px; gap: 8px; }
  .aiw-header .logo span,
  .aiw-logo span { font-size: 13px; }
  .aiw-header .class-badge { display: none; }
  .aiw-header .user-info { display: none; }
  .aiw-header .btn-logout span { display: none; }
  .aiw-header .btn-logout { padding: 5px 8px; }

  /* Tool header */
  .tool-header { padding: 0 12px; gap: 8px; }
  .tool-header h1 { font-size: 13px; }
  .tool-header .tool-badge { display: none; }
  .tool-header .back-link span { display: none; }

  /* Chapter tool cards — stack */
  .chapter-tool-cards { grid-template-columns: 1fr; }
}
@media (max-width: 480px) {
  .tools-grid { grid-template-columns: 1fr; }
  .progress-grid { grid-template-columns: 1fr; }
  .welcome-hero h1 { font-size: 18px; }
  .aiw-header .logo { font-size: 12px; }
}