@import url('https://fonts.googleapis.com/css2?family=Fredoka:wght@400;500;600;700&family=Nunito:ital,wght@0,400;0,500;0,600;0,700;1,400&family=JetBrains+Mono:wght@400;500&display=swap');

/* ── TOKENS ─────────────────────────────────────────────────────────── */
:root {
  /* dark mode — deep navy / networking blue */
  --bg:           #0F1623;
  --surface:      #161E2E;
  --card:         #1C2540;
  --card-hover:   #22304E;
  --border:       #2A3A5C;
  --border-mid:   #3A5080;
  --text:         #E8F0FF;
  --text-muted:   #7A97C8;
  --text-dim:     #4A6088;
  --accent:       #3B82F6;
  --accent-hover: #60A5FA;
  --accent-dim:   rgba(59,130,246,0.18);
  --success:      #22C55E;
  --success-dim:  rgba(34,197,94,0.18);
  --error:        #EF4444;
  --error-dim:    rgba(239,68,68,0.18);
  --warning:      #F59E0B;
  --warning-dim:  rgba(245,158,11,0.18);
  --locked:       #131B2E;
  --locked-text:  #4A6088;
  --radius:       20px;
  --radius-sm:    14px;
  --radius-pill:  999px;
  --font-sans:    'Nunito', sans-serif;
  --font-display: 'Fredoka', sans-serif;
  --font-mono:    'JetBrains Mono', 'Fira Code', monospace;
  --shadow:       0 4px 24px rgba(0,0,0,0.55);
  --shadow-sm:    0 2px 10px rgba(0,0,0,0.38);
  --transition:   200ms ease;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg:          #F0F6FF;
    --surface:     #FFFFFF;
    --card:        #F8FBFF;
    --card-hover:  #EEF4FF;
    --border:      #C5D8F0;
    --border-mid:  #A8C4E8;
    --text:        #1A2744;
    --text-muted:  #4A6088;
    --text-dim:    #92AACB;
    --locked:      #E8F0FF;
    --locked-text: #92AACB;
    --accent-dim:  rgba(59,130,246,0.12);
    --success-dim: rgba(34,197,94,0.12);
    --error-dim:   rgba(239,68,68,0.12);
    --warning-dim: rgba(245,158,11,0.13);
    --shadow:      0 4px 20px rgba(26,39,68,0.11), 0 1px 4px rgba(26,39,68,0.06);
    --shadow-sm:   0 2px 10px rgba(26,39,68,0.08);
  }
}

/* ── RESET ───────────────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { height: 100%; height: 100dvh; font-size: 16px; }
body {
  height: 100%;
  height: 100dvh;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  overflow: hidden;
}
button { cursor: pointer; font-family: inherit; border: none; background: none; }
a { color: inherit; text-decoration: none; }

/* ── APP WRAPPER ─────────────────────────────────────────────────────── */
#app {
  position: fixed;
  inset: 0;
  max-width: 600px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
}

/* ── SCREENS ─────────────────────────────────────────────────────────── */
.screen {
  display: none;
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  -webkit-overflow-scrolling: touch;
}
.screen.active {
  display: flex;
  flex-direction: column;
  animation: screenIn 0.32s cubic-bezier(0.22, 1, 0.36, 1) both;
}
#screen-activity.active, #screen-lesson.active {
  overflow: hidden;
}
#screen-home.active, #screen-topic.active {
  overflow-y: auto;
}
@keyframes screenIn {
  from { opacity: 0; transform: translateY(18px) scale(0.99); }
  to   { opacity: 1; transform: translateY(0) scale(1); }
}

/* ── HOME SCREEN ─────────────────────────────────────────────────────── */
.home-header {
  padding: 28px 24px 24px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: relative;
  overflow: hidden;
  flex-shrink: 0;
}
.home-header::before {
  content: '';
  position: absolute;
  top: -60px; right: -40px;
  width: 280px; height: 280px;
  background: radial-gradient(circle, var(--accent-dim) 0%, transparent 68%);
  pointer-events: none;
}
.home-brand {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 22px;
  position: relative;
}
.home-brand svg { flex-shrink: 0; }
.home-brand-text h1 {
  font-family: var(--font-display);
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.1;
}
.home-brand-text span {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
}
.home-stats {
  display: flex;
  gap: 10px;
  margin-bottom: 18px;
  flex-wrap: wrap;
}
.stat-chip {
  display: flex;
  align-items: center;
  gap: 6px;
  background: var(--card);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-pill);
  padding: 7px 16px;
  font-size: 0.9rem;
  font-weight: 700;
  font-family: var(--font-display);
}
.stat-chip.accent { background: var(--accent-dim); border-color: var(--accent); color: var(--accent); }
.stat-chip.fire   { background: var(--warning-dim); border-color: var(--warning); color: var(--warning); }

.overall-progress { margin-bottom: 4px; }
.overall-progress-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 8px;
}
.progress-bar-track {
  height: 10px;
  background: var(--border);
  border-radius: var(--radius-pill);
  overflow: hidden;
}
.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent) 0%, #60A5FA 100%);
  border-radius: var(--radius-pill);
  transition: width 0.7s cubic-bezier(0.22, 1, 0.36, 1);
}
.home-continue-btn { margin-top: 16px; }

.topic-grid {
  padding: 16px 24px;
  padding-bottom: max(40px, calc(24px + env(safe-area-inset-bottom)));
  display: flex;
  flex-direction: column;
  gap: 10px;
  flex-shrink: 0;
}
.part-label {
  font-family: var(--font-display);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-top: 10px;
  margin-bottom: 2px;
  padding-left: 2px;
}

.topic-card {
  background: var(--card);
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition),
              transform var(--transition), box-shadow var(--transition);
  display: flex;
  align-items: center;
  gap: 14px;
  user-select: none;
}
.topic-card:hover:not(.locked) { background: var(--card-hover); border-color: var(--border-mid); box-shadow: var(--shadow-sm); transform: translateY(-1px); }
.topic-card:active:not(.locked) { transform: scale(0.98) translateY(0); }
.topic-card.locked { cursor: default; opacity: 0.5; }
.topic-card.complete { border-color: var(--success); }
.topic-card.complete .topic-card-icon { background: var(--success-dim); color: var(--success); }

.topic-card[data-part="1"]  .topic-card-icon { background: rgba(59,130,246,0.16);  color: #3B82F6; }
.topic-card[data-part="2"]  .topic-card-icon { background: rgba(34,197,94,0.16);   color: #22C55E; }
.topic-card[data-part="3"]  .topic-card-icon { background: rgba(168,85,247,0.16);  color: #A855F7; }
.topic-card[data-part="4"]  .topic-card-icon { background: rgba(245,158,11,0.16);  color: #F59E0B; }
.topic-card[data-part="5"]  .topic-card-icon { background: rgba(239,68,68,0.16);   color: #EF4444; }
.topic-card[data-part="6"]  .topic-card-icon { background: rgba(20,184,166,0.16);  color: #14B8A6; }
.topic-card[data-part="7"]  .topic-card-icon { background: rgba(249,115,22,0.16);  color: #F97316; }
.topic-card[data-part="8"]  .topic-card-icon { background: rgba(99,102,241,0.16);  color: #6366F1; }
.topic-card[data-part="9"]  .topic-card-icon { background: rgba(236,72,153,0.16);  color: #EC4899; }
.topic-card[data-part="10"] .topic-card-icon { background: rgba(16,185,129,0.16);  color: #10B981; }

.topic-card-icon {
  width: 46px; height: 46px;
  border-radius: var(--radius-sm);
  background: var(--accent-dim);
  color: var(--accent);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.25rem;
  flex-shrink: 0;
  transition: all var(--transition);
}
.topic-card.locked .topic-card-icon { background: var(--locked); color: var(--locked-text); }
.topic-card-body { flex: 1; min-width: 0; }
.topic-card-title { font-size: 0.97rem; font-weight: 700; line-height: 1.2; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topic-card.locked .topic-card-title { color: var(--locked-text); }
.topic-card-meta { font-size: 0.76rem; color: var(--text-muted); margin-top: 3px; font-weight: 500; }
.topic-card-progress { display: flex; flex-direction: column; align-items: flex-end; gap: 4px; flex-shrink: 0; }
.topic-card-dots { display: flex; gap: 4px; }
.dot { width: 8px; height: 8px; border-radius: 50%; background: var(--border-mid); }
.dot.done    { background: var(--success); }
.dot.current { background: var(--accent); }

/* ── TOPIC SCREEN ────────────────────────────────────────────────────── */
.screen-header {
  display: flex; align-items: center; gap: 12px;
  padding: 16px 24px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}
.btn-back {
  width: 40px; height: 40px;
  border-radius: 50%;
  background: var(--card);
  border: 1.5px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  color: var(--text);
  font-size: 1.05rem; font-weight: 700;
  transition: background var(--transition), box-shadow var(--transition);
  flex-shrink: 0;
}
.btn-back:hover { background: var(--card-hover); box-shadow: var(--shadow-sm); }
.screen-header-text { flex: 1; min-width: 0; }
.screen-header-text h2 { font-family: var(--font-display); font-size: 1.2rem; font-weight: 600; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.screen-header-text p { font-size: 0.78rem; color: var(--text-muted); font-weight: 500; }

.topic-hero { padding: 22px 24px; background: var(--surface); border-bottom: 1px solid var(--border); }
.part-badge {
  display: inline-flex; align-items: center;
  background: var(--accent); color: #fff;
  font-size: 0.72rem; font-weight: 700; font-family: var(--font-display);
  letter-spacing: 0.06em; text-transform: uppercase;
  padding: 4px 12px; border-radius: var(--radius-pill); margin-bottom: 12px;
}
.topic-description { font-size: 0.92rem; color: var(--text-muted); font-weight: 500; line-height: 1.55; }
.topic-study-btn { margin-top: 14px; width: 100%; }

.activity-list { padding: 16px 24px; display: flex; flex-direction: column; gap: 8px; }
.activity-list-item {
  display: flex; align-items: center; gap: 12px;
  padding: 12px 14px;
  background: var(--card);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.875rem; font-weight: 500;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition),
              transform var(--transition), box-shadow var(--transition);
}
.activity-list-item:hover { background: var(--card-hover); border-color: var(--border-mid); transform: translateX(2px); box-shadow: var(--shadow-sm); }
.activity-list-item.done { border-color: var(--success); }
.activity-list-item.done:hover { border-color: var(--success); background: var(--success-dim); }
.activity-dot {
  width: 26px; height: 26px; border-radius: 50%;
  border: 2px solid var(--border-mid);
  display: flex; align-items: center; justify-content: center;
  font-size: 0.68rem; font-weight: 700; flex-shrink: 0;
  color: var(--text-muted); font-family: var(--font-display);
}
.activity-dot.done    { background: var(--success); border-color: var(--success); color: #fff; font-size: 0.78rem; }
.activity-dot.current { border-color: var(--accent); color: var(--accent); }

.activity-type-badge {
  margin-left: auto;
  font-size: 0.67rem; font-weight: 700; font-family: var(--font-display);
  letter-spacing: 0.04em; color: var(--text-muted);
  background: var(--bg); border: 1.5px solid var(--border);
  border-radius: var(--radius-pill); padding: 3px 10px;
  white-space: nowrap; flex-shrink: 0;
}
.activity-type-badge.type-multiple_choice { background: rgba(59,130,246,0.14);  color: #3B82F6; border-color: rgba(59,130,246,0.35); }
.activity-type-badge.type-drag_fill       { background: rgba(168,85,247,0.13);  color: #A855F7; border-color: rgba(168,85,247,0.35); }
.activity-type-badge.type-code_ordering   { background: rgba(34,197,94,0.13);   color: #22C55E; border-color: rgba(34,197,94,0.35); }
.activity-type-badge.type-spot_bug        { background: rgba(239,68,68,0.13);   color: #EF4444; border-color: rgba(239,68,68,0.35); }
.activity-type-badge.type-true_false      { background: rgba(245,158,11,0.13);  color: #F59E0B; border-color: rgba(245,158,11,0.35); }
.activity-type-badge.type-mini_game       { background: rgba(20,184,166,0.13);  color: #14B8A6; border-color: rgba(20,184,166,0.35); }

.topic-footer {
  padding: 16px 24px;
  padding-bottom: max(24px, calc(16px + env(safe-area-inset-bottom)));
  border-top: 1px solid var(--border);
  background: var(--surface);
}
.topic-footer-actions { display: flex; gap: 10px; flex-wrap: wrap; }
.topic-footer-actions .btn { flex: 1; min-width: 0; }

/* ── ACTIVITY SCREEN ─────────────────────────────────────────────────── */
.activity-progress-bar { height: 6px; background: var(--border); flex-shrink: 0; }
.activity-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent) 0%, #60A5FA 100%);
  transition: width 0.45s cubic-bezier(0.22, 1, 0.36, 1);
}
.activity-step {
  padding: 8px 20px 8px 14px;
  font-size: 0.78rem; font-weight: 600; color: var(--text-muted);
  flex-shrink: 0; background: var(--surface);
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; gap: 10px;
}
.activity-step-count { flex: 1; }
.activity-step-type {
  font-size: 0.7rem; font-weight: 700; font-family: var(--font-display);
  letter-spacing: 0.05em; text-transform: uppercase; color: var(--accent);
}
.btn-back-activity {
  width: 36px; height: 36px; border-radius: 50%;
  background: var(--card); border: 1.5px solid var(--border-mid);
  color: var(--text);
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0; font-weight: 700;
  transition: background var(--transition), box-shadow var(--transition);
}
.btn-back-activity:hover { background: var(--card-hover); box-shadow: var(--shadow-sm); }

.activity-body {
  flex: 1; min-height: 0;
  overflow-y: auto; -webkit-overflow-scrolling: touch;
  padding: 22px 24px;
  display: flex; flex-direction: column; gap: 18px;
}
.activity-question { font-size: 1.05rem; font-weight: 600; line-height: 1.55; }

/* ── CODE BLOCK ─────────────────────────────────────────────────────── */
.code-block { background: #0D1117; border: 1px solid #21262D; border-radius: var(--radius-sm); }
.code-block pre[class*="language-"] {
  margin: 0; padding: 16px; background: transparent !important;
  font-family: var(--font-mono); font-size: 0.82rem;
  line-height: 1.6; tab-size: 4;
  white-space: pre-wrap; word-break: break-all; overflow: visible;
}
.code-block-plain {
  background: #0D1117; border: 1px solid #21262D; border-radius: var(--radius-sm);
  padding: 14px 16px; font-family: var(--font-mono); font-size: 0.82rem;
  line-height: 1.8; color: #C9D1D9; white-space: pre-wrap; word-break: break-all;
}

/* ── MULTIPLE CHOICE ─────────────────────────────────────────────────── */
.mc-options { display: flex; flex-direction: column; gap: 10px; }
.mc-option {
  display: flex; align-items: flex-start; gap: 14px;
  padding: 14px 16px; background: var(--card);
  border: 1.5px solid var(--border); border-radius: var(--radius-sm);
  cursor: pointer; text-align: left;
  font-size: 0.92rem; font-weight: 500; line-height: 1.45; color: var(--text);
  transition: background var(--transition), border-color var(--transition),
              box-shadow var(--transition), transform var(--transition); width: 100%;
}
.mc-option:hover:not(:disabled) { background: var(--card-hover); border-color: var(--border-mid); box-shadow: var(--shadow-sm); transform: translateX(2px); }
.mc-option:disabled { cursor: default; }
.mc-option.selected { background: var(--accent-dim); border-color: var(--accent); }
.mc-option.correct  { background: var(--success-dim); border-color: var(--success); }
.mc-option.wrong    { background: var(--error-dim); border-color: var(--error); animation: shake 0.42s ease; }
.mc-letter {
  width: 30px; height: 30px; border-radius: 50%;
  background: var(--bg); border: 1.5px solid var(--border-mid);
  color: var(--text); display: flex; align-items: center; justify-content: center;
  font-size: 0.8rem; font-weight: 700; flex-shrink: 0; font-family: var(--font-display);
  transition: all var(--transition);
}
.mc-option.selected .mc-letter { background: var(--accent); border-color: var(--accent); color: #fff; }
.mc-option.correct .mc-letter  { background: var(--success); border-color: var(--success); color: #fff; }
.mc-option.wrong .mc-letter    { background: var(--error); border-color: var(--error); color: #fff; }

/* ── TRUE/FALSE ──────────────────────────────────────────────────────── */
.tf-buttons { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.btn-tf {
  padding: 18px; border-radius: var(--radius);
  font-size: 1.05rem; font-weight: 700; font-family: var(--font-display);
  border: 1.5px solid var(--border-mid); background: var(--card); color: var(--text);
  transition: all var(--transition);
}
.btn-tf:hover:not(:disabled) { background: var(--card-hover); box-shadow: var(--shadow-sm); transform: translateY(-1px); }
.btn-tf.selected { background: var(--accent-dim); border-color: var(--accent); color: var(--accent); }
.btn-tf.correct  { background: var(--success-dim); border-color: var(--success); color: var(--success); }
.btn-tf.wrong    { background: var(--error-dim); border-color: var(--error); color: var(--error); animation: shake 0.42s ease; }

/* ── DRAG-TO-FILL ────────────────────────────────────────────────────── */
.drag-fill-code {
  background: #0D1117; border: 1px solid #21262D; border-radius: var(--radius-sm);
  padding: 14px 16px; font-family: var(--font-mono); font-size: 0.82rem;
  line-height: 2; color: #C9D1D9; white-space: pre-wrap; word-break: break-word;
}
.blank-slot {
  display: inline-block; min-width: 58px; height: 28px; line-height: 28px;
  padding: 0 10px; background: #1C2333; border: 1.5px dashed #3A5080;
  border-radius: 8px; cursor: pointer; text-align: center; vertical-align: middle;
  font-size: 0.75rem; color: #4A6088; transition: all var(--transition); position: relative;
}
.blank-slot.has-value  { background: #0D2B1A; border-color: var(--success); border-style: solid; color: #6EE7B7; }
.blank-slot.drag-over  { background: #0D1E3B; border-color: var(--accent); color: var(--accent); transform: scale(1.07); }
.blank-slot.correct    { background: var(--success-dim); border-color: var(--success); border-style: solid; color: #6EE7B7; }
.blank-slot.wrong      { background: var(--error-dim); border-color: var(--error); border-style: solid; color: #FCA5A5; }

.tokens-area {
  display: flex; flex-wrap: wrap; align-content: flex-start;
  flex-shrink: 0; gap: 8px; padding: 10px 14px;
  background: var(--card); border: 1.5px solid var(--border);
  border-radius: var(--radius-sm); min-height: 56px;
}
.tokens-area .token {
  display: flex; align-items: center; padding: 5px 16px;
  background: var(--surface); border: 1.5px solid var(--border-mid);
  border-radius: var(--radius-pill); font-family: var(--font-mono);
  font-size: 0.82rem; font-weight: 500; cursor: grab;
  user-select: none; transition: all var(--transition); touch-action: none;
}
.tokens-area .token:hover { background: var(--card-hover); border-color: var(--accent); color: var(--accent); box-shadow: var(--shadow-sm); }
.tokens-area .token.being-dragged { opacity: 0.3; }
.tokens-area .token.used { opacity: 0.3; pointer-events: none; }
.tokens-area .token.selected-mobile { background: var(--accent-dim); border-color: var(--accent); color: var(--accent); box-shadow: 0 0 0 3px var(--accent-dim); }

/* ── CODE ORDERING ───────────────────────────────────────────────────── */
.code-lines-list {
  display: flex; flex-direction: column; gap: 5px; padding: 6px;
  background: #0D1117; border: 1px solid #21262D; border-radius: var(--radius-sm);
}
.code-line-item {
  display: flex; align-items: center; gap: 10px; padding: 9px 12px;
  background: #161B27; border: 1px solid #21262D; border-radius: 10px;
  cursor: grab; touch-action: none; user-select: none; overflow-x: auto;
  transition: background var(--transition), border-color var(--transition), transform var(--transition);
}
.code-line-item:hover { background: #1C2333; border-color: #3A5080; transform: translateX(2px); }
.code-line-item.dragging-line { opacity: 0.3; }
.code-line-item.drop-target   { border-color: var(--accent); background: #0D1E3B; }
.code-line-item.correct-line  { border-color: var(--success); background: #0D2B1A; }
.code-line-item.wrong-line    { border-color: var(--error);   background: #2B0D0D; }
.drag-handle { color: #3A5080; font-size: 0.85rem; cursor: grab; flex-shrink: 0; }
.code-line-text { font-family: var(--font-mono); font-size: 0.8rem; color: #C9D1D9; white-space: pre; flex-shrink: 0; }

/* ── SPOT THE BUG ────────────────────────────────────────────────────── */
.bug-label { font-size: 0.78rem; font-weight: 700; font-family: var(--font-display); color: var(--error); text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 4px; }
.fixed-code-label { font-size: 0.78rem; font-weight: 700; font-family: var(--font-display); color: var(--success); text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 4px; margin-top: 12px; }

/* ── RESULT PANEL ────────────────────────────────────────────────────── */
.result-panel {
  border-top: 1.5px solid var(--border);
  padding: 16px 0 4px;
  display: flex; flex-direction: column; gap: 12px;
  animation: slideUp 0.38s cubic-bezier(0.22, 1, 0.36, 1) both;
}
@keyframes slideUp { from { transform: translateY(20px); opacity: 0; } to { transform: translateY(0); opacity: 1; } }
.xp-earned {
  display: inline-flex; align-items: center; gap: 4px;
  background: var(--warning-dim); color: var(--warning);
  border: 1.5px solid var(--warning); border-radius: var(--radius-pill);
  padding: 3px 12px; font-size: 0.82rem; font-weight: 700; font-family: var(--font-display); margin-left: 4px;
}
.result-explanation {
  font-size: 0.9rem; line-height: 1.65; color: var(--text-muted); font-weight: 500;
  padding: 14px; background: var(--card); border: 1.5px solid var(--border); border-radius: var(--radius-sm);
}
.result-explanation code {
  font-family: var(--font-mono); font-size: 0.8rem;
  background: var(--bg); padding: 1px 6px; border-radius: 6px; color: var(--accent);
}

/* ── BUTTONS ─────────────────────────────────────────────────────────── */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 14px 28px; border-radius: var(--radius-pill);
  font-size: 1rem; font-weight: 700; font-family: var(--font-display);
  transition: all var(--transition); cursor: pointer; border: none; width: 100%;
}
.btn-primary { background: var(--accent); color: #fff; box-shadow: 0 4px 14px rgba(59,130,246,0.35); }
.btn-primary:hover { background: var(--accent-hover); transform: translateY(-1px); box-shadow: 0 6px 20px rgba(59,130,246,0.44); }
.btn-primary:active { transform: scale(0.97) translateY(0); }
.btn-primary:disabled { background: var(--border-mid); color: var(--text-dim); cursor: not-allowed; box-shadow: none; }
.btn-secondary { background: var(--card); color: var(--text); border: 1.5px solid var(--border-mid); }
.btn-secondary:hover { background: var(--card-hover); border-color: var(--text-muted); box-shadow: var(--shadow-sm); }

.activity-footer {
  padding: 14px 24px;
  padding-bottom: max(14px, calc(10px + env(safe-area-inset-bottom)));
  background: var(--surface); border-top: 1px solid var(--border); flex-shrink: 0;
}
.result-footer-bar { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.result-footer-bar.correct { --result-color: var(--success); }
.result-footer-bar.wrong   { --result-color: var(--error); }
.result-footer-left { display: flex; align-items: center; gap: 8px; flex-shrink: 0; }
.result-footer-icon {
  width: 30px; height: 30px; border-radius: 50%;
  background: color-mix(in srgb, var(--result-color) 15%, transparent);
  border: 1.5px solid var(--result-color); color: var(--result-color);
  display: flex; align-items: center; justify-content: center;
  font-size: 0.9rem; font-weight: 700; flex-shrink: 0;
}
.result-footer-label { font-family: var(--font-display); font-size: 1rem; font-weight: 700; color: var(--result-color); }

/* ── TOPIC COMPLETE ──────────────────────────────────────────────────── */
.topic-complete { display: flex; flex-direction: column; align-items: center; gap: 18px; padding: 48px 24px; text-align: center; flex: 1; }
.topic-complete-icon { font-size: 5rem; animation: bounce 0.9s ease-in-out infinite alternate; }
@keyframes bounce { from { transform: translateY(0) scale(1); } to { transform: translateY(-18px) scale(1.06); } }
.topic-complete h2 { font-family: var(--font-display); font-size: 2rem; font-weight: 700; color: var(--accent); }
.topic-complete p { color: var(--text-muted); max-width: 320px; font-weight: 500; font-size: 0.95rem; }
.xp-big { font-family: var(--font-display); font-size: 2.5rem; font-weight: 700; color: var(--warning); animation: popIn 0.55s cubic-bezier(0.34, 1.56, 0.64, 1); }
@keyframes popIn { 0% { transform: scale(0.3); opacity: 0; } 60% { transform: scale(1.18); opacity: 1; } 80% { transform: scale(0.94); } 100% { transform: scale(1); } }

/* ── ANIMATIONS ──────────────────────────────────────────────────────── */
@keyframes shake { 0%, 100% { transform: translateX(0); } 20% { transform: translateX(-7px); } 40% { transform: translateX(7px); } 60% { transform: translateX(-4px); } 80% { transform: translateX(4px); } }

/* ── UTILITIES ───────────────────────────────────────────────────────── */
.mt-4  { margin-top: 4px; }
.mt-8  { margin-top: 8px; }
.mt-12 { margin-top: 12px; }
.text-muted  { color: var(--text-muted); font-size: 0.85rem; }
.text-center { text-align: center; }

/* ── PRISM OVERRIDE ──────────────────────────────────────────────────── */
code[class*="language-"], pre[class*="language-"] { font-family: var(--font-mono) !important; font-size: 0.82rem !important; }
.token.keyword    { color: #ff7b72 !important; }
.token.string     { color: #a5d6ff !important; }
.token.comment    { color: #8b949e !important; font-style: italic; }
.token.number     { color: #79c0ff !important; }
.token.operator   { color: #ff7b72 !important; }
.token.function   { color: #d2a8ff !important; }
.token.punctuation { color: #c9d1d9 !important; }

/* ── SCROLLBAR ───────────────────────────────────────────────────────── */
::-webkit-scrollbar { width: 4px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border-mid); border-radius: 4px; }

/* ── INSTALL BANNER ──────────────────────────────────────────────────── */
#install-banner {
  display: none; align-items: center; gap: 10px; padding: 10px 18px;
  background: var(--accent-dim); border-bottom: 1.5px solid var(--accent);
  font-size: 0.84rem; font-weight: 600; flex-shrink: 0;
}
#install-banner.visible { display: flex; }
#install-banner button {
  margin-left: auto; background: var(--accent); color: #fff;
  padding: 6px 16px; border-radius: var(--radius-pill);
  font-size: 0.82rem; font-weight: 700; font-family: var(--font-display);
  white-space: nowrap; flex-shrink: 0;
}

/* ══════════════════════════════════════════════════════════════════════
   LESSON SCREEN
   ══════════════════════════════════════════════════════════════════════ */
.lesson-header { flex-shrink: 0; padding: 14px 20px 0; border-bottom: 1px solid var(--border); background: var(--surface); }
.lesson-header-row { display: flex; align-items: center; gap: 12px; padding-bottom: 12px; }
.lesson-title-group { flex: 1; min-width: 0; }
.lesson-topic-name { font-size: 0.75rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.06em; }
.lesson-counter { font-size: 0.85rem; font-weight: 700; color: var(--text); font-family: var(--font-display); }
.lesson-progress-bar { height: 3px; background: var(--border); border-radius: var(--radius-pill); overflow: hidden; }
.lesson-progress-fill { height: 100%; background: var(--accent); border-radius: var(--radius-pill); transition: width 0.35s ease; }

.lesson-body { flex: 1; min-height: 0; overflow-y: auto; -webkit-overflow-scrolling: touch; padding: 24px 20px; display: flex; flex-direction: column; gap: 16px; }
.lesson-card { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px 20px; display: flex; flex-direction: column; gap: 14px; }
.lesson-card-title { font-family: var(--font-display); font-size: 1.25rem; font-weight: 600; color: var(--text); line-height: 1.3; }
.lesson-card-body { font-size: 0.95rem; line-height: 1.7; color: var(--text); }
.lesson-card-body code { font-family: var(--font-mono); font-size: 0.88em; background: var(--bg); border: 1px solid var(--border); border-radius: 5px; padding: 1px 5px; color: var(--accent); }
.lesson-card-body p + p { margin-top: 10px; }
.lesson-code-block { background: #0D1117; border: 1px solid #21262D; border-radius: var(--radius-sm); overflow-x: auto; }
.lesson-code-block pre[class*="language-"] { margin: 0; padding: 14px 16px; font-size: 0.85rem; line-height: 1.6; white-space: pre-wrap; word-break: break-all; overflow: visible; background: transparent !important; }
.lesson-tip { display: flex; gap: 10px; background: var(--accent-dim); border: 1px solid rgba(59,130,246,0.25); border-radius: var(--radius-sm); padding: 12px 14px; font-size: 0.875rem; line-height: 1.6; color: var(--text); }
.lesson-tip-icon { flex-shrink: 0; font-size: 1rem; margin-top: 1px; }
.lesson-tip code { font-family: var(--font-mono); font-size: 0.85em; color: var(--accent); }

.lesson-footer { flex-shrink: 0; padding: 14px 20px; padding-bottom: max(14px, calc(10px + env(safe-area-inset-bottom))); background: var(--surface); border-top: 1px solid var(--border); display: flex; gap: 10px; }
.lesson-footer .btn { flex: 1; }
.lesson-footer .btn-prev { background: var(--card); border: 1px solid var(--border); color: var(--text); font-family: var(--font-display); font-size: 1rem; font-weight: 600; padding: 14px 20px; border-radius: var(--radius-pill); cursor: pointer; transition: background var(--transition), border-color var(--transition); }
.lesson-footer .btn-prev:hover:not(:disabled) { background: var(--card-hover); border-color: var(--border-mid); }
.lesson-footer .btn-prev:disabled { opacity: 0.35; cursor: not-allowed; }

/* ══════════════════════════════════════════════════════════════════════
   MINI GAME STYLES
   ══════════════════════════════════════════════════════════════════════ */
.mini-game-container {
  display: flex; flex-direction: column; gap: 16px;
}

/* ── Layer Sort Game ─────────────────────────────────────────────────── */
.layer-sort-items {
  display: flex; flex-wrap: wrap; gap: 8px;
  padding: 14px; background: var(--card); border: 1.5px solid var(--border); border-radius: var(--radius-sm);
  min-height: 52px;
}
.layer-sort-item {
  padding: 6px 14px; background: var(--surface); border: 1.5px solid var(--border-mid);
  border-radius: var(--radius-pill); font-size: 0.82rem; font-weight: 600;
  cursor: grab; user-select: none; touch-action: none;
  transition: all var(--transition);
}
.layer-sort-item:hover { border-color: var(--accent); color: var(--accent); background: var(--card-hover); }
.layer-sort-item.placed { opacity: 0.4; pointer-events: none; }

.layer-sort-buckets { display: flex; flex-direction: column; gap: 6px; }
.layer-bucket {
  display: flex; align-items: flex-start; gap: 10px;
  padding: 10px 12px; background: var(--card); border: 1.5px dashed var(--border-mid);
  border-radius: var(--radius-sm); min-height: 48px; transition: border-color var(--transition), background var(--transition);
}
.layer-bucket.drag-over { border-color: var(--accent); background: var(--accent-dim); }
.layer-bucket.correct   { border-color: var(--success) !important; border-style: solid; background: var(--success-dim); }
.layer-bucket.wrong     { border-color: var(--error) !important; border-style: solid; background: var(--error-dim); }
.layer-bucket-label {
  font-size: 0.75rem; font-weight: 700; font-family: var(--font-display);
  color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em;
  white-space: nowrap; flex-shrink: 0; padding-top: 2px;
  min-width: 90px;
}
.layer-bucket-items { display: flex; flex-wrap: wrap; gap: 6px; flex: 1; }
.layer-bucket-chip {
  padding: 4px 10px; background: var(--accent-dim); border: 1px solid var(--accent);
  border-radius: var(--radius-pill); font-size: 0.76rem; font-weight: 600; color: var(--accent);
}

/* ── Port Match Game ─────────────────────────────────────────────────── */
.port-match-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.port-match-service {
  padding: 12px 14px; background: var(--card); border: 1.5px solid var(--border);
  border-radius: var(--radius-sm); font-size: 0.88rem; font-weight: 600;
  cursor: pointer; transition: all var(--transition); text-align: center;
}
.port-match-service.selected { background: var(--accent-dim); border-color: var(--accent); color: var(--accent); }
.port-match-service.matched  { background: var(--success-dim); border-color: var(--success); color: var(--success); pointer-events: none; }
.port-match-service.wrong    { animation: shake 0.42s ease; background: var(--error-dim); border-color: var(--error); }
.port-match-ports { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; }
.port-match-port {
  padding: 8px 16px; background: var(--card); border: 1.5px solid var(--border-mid);
  border-radius: var(--radius-pill); font-family: var(--font-mono); font-size: 0.85rem; font-weight: 600;
  cursor: pointer; transition: all var(--transition);
}
.port-match-port:hover:not(.matched):not(:disabled) { border-color: var(--accent); color: var(--accent); }
.port-match-port.matched { background: var(--success-dim); border-color: var(--success); color: var(--success); pointer-events: none; }

/* ── Protocol Sort Game ──────────────────────────────────────────────── */
.protocol-sort-items {
  display: flex; flex-wrap: wrap; gap: 8px;
  padding: 14px; background: var(--card); border: 1.5px solid var(--border); border-radius: var(--radius-sm);
}
.protocol-sort-item {
  padding: 6px 14px; background: var(--surface); border: 1.5px solid var(--border-mid);
  border-radius: var(--radius-pill); font-size: 0.82rem; font-weight: 600;
  cursor: grab; user-select: none; touch-action: none; transition: all var(--transition);
}
.protocol-sort-item:hover { border-color: var(--accent); color: var(--accent); }
.protocol-sort-item.placed { opacity: 0.35; pointer-events: none; }
.protocol-sort-buckets { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.protocol-sort-bucket {
  padding: 10px 12px; background: var(--card); border: 1.5px dashed var(--border-mid);
  border-radius: var(--radius-sm); min-height: 80px; transition: all var(--transition);
}
.protocol-sort-bucket.drag-over { border-color: var(--accent); background: var(--accent-dim); }
.protocol-sort-bucket.correct   { border-color: var(--success) !important; border-style: solid; background: var(--success-dim); }
.protocol-sort-bucket.wrong     { border-color: var(--error) !important; border-style: solid; background: var(--error-dim); }
.protocol-sort-bucket-label { font-size: 0.72rem; font-weight: 700; font-family: var(--font-display); text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-muted); margin-bottom: 8px; }
.protocol-sort-bucket-items { display: flex; flex-wrap: wrap; gap: 5px; }
.protocol-sort-chip { padding: 3px 10px; background: var(--accent-dim); border: 1px solid var(--accent); border-radius: var(--radius-pill); font-size: 0.72rem; font-weight: 600; color: var(--accent); }

/* ── TCP Handshake Game ──────────────────────────────────────────────── */
.tcp-handshake-diagram { display: flex; gap: 16px; align-items: flex-start; }
.tcp-peer { flex: 1; display: flex; flex-direction: column; align-items: center; gap: 8px; }
.tcp-peer-label { font-family: var(--font-display); font-size: 0.85rem; font-weight: 700; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.06em; }
.tcp-peer-line { width: 2px; height: 120px; background: var(--border-mid); }
.tcp-steps { display: flex; flex-direction: column; gap: 8px; margin: 8px 0; }
.tcp-step-btn {
  padding: 10px 16px; background: var(--card); border: 1.5px solid var(--border);
  border-radius: var(--radius-sm); font-size: 0.85rem; font-weight: 600;
  cursor: pointer; transition: all var(--transition); display: flex; align-items: center; gap: 8px;
}
.tcp-step-btn:hover:not(:disabled):not(.done-step) { border-color: var(--accent); background: var(--accent-dim); color: var(--accent); }
.tcp-step-btn.active-step { border-color: var(--accent); background: var(--accent-dim); color: var(--accent); }
.tcp-step-btn.done-step   { border-color: var(--success); background: var(--success-dim); color: var(--success); pointer-events: none; }
.tcp-step-btn.wrong-step  { border-color: var(--error); background: var(--error-dim); color: var(--error); animation: shake 0.42s ease; }
.tcp-arrow { font-size: 0.9rem; }

/* ── Binary Convert Game ─────────────────────────────────────────────── */
.binary-round {
  padding: 16px; background: var(--card); border: 1.5px solid var(--border); border-radius: var(--radius);
  display: flex; flex-direction: column; gap: 12px;
}
.binary-question { font-size: 0.85rem; font-weight: 600; color: var(--text-muted); text-align: center; }
.binary-value {
  font-family: var(--font-mono); font-size: 2rem; font-weight: 700;
  color: var(--accent); text-align: center; letter-spacing: 0.05em;
}
.binary-input-row { display: flex; gap: 8px; }
.binary-input {
  flex: 1; padding: 12px 14px; background: var(--bg); border: 1.5px solid var(--border-mid);
  border-radius: var(--radius-sm); font-family: var(--font-mono); font-size: 1rem;
  color: var(--text); outline: none; transition: border-color var(--transition);
}
.binary-input:focus { border-color: var(--accent); }
.binary-input.correct { border-color: var(--success); background: var(--success-dim); }
.binary-input.wrong   { border-color: var(--error); background: var(--error-dim); animation: shake 0.42s ease; }
.binary-check-btn {
  padding: 12px 18px; background: var(--accent); color: #fff;
  border-radius: var(--radius-sm); font-family: var(--font-display); font-size: 0.95rem;
  font-weight: 700; transition: all var(--transition); flex-shrink: 0;
}
.binary-check-btn:hover { background: var(--accent-hover); }
.binary-progress-dots { display: flex; gap: 6px; justify-content: center; }
.binary-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--border-mid); transition: background var(--transition); }
.binary-dot.done    { background: var(--success); }
.binary-dot.current { background: var(--accent); }

/* ── Subnet Calc Game ────────────────────────────────────────────────── */
.subnet-display {
  padding: 16px; background: var(--card); border: 1.5px solid var(--border);
  border-radius: var(--radius); text-align: center;
}
.subnet-ip { font-family: var(--font-mono); font-size: 1.5rem; font-weight: 700; color: var(--accent); }
.subnet-fields { display: flex; flex-direction: column; gap: 10px; }
.subnet-field { display: flex; align-items: center; gap: 10px; }
.subnet-field-label { font-size: 0.8rem; font-weight: 700; color: var(--text-muted); min-width: 110px; font-family: var(--font-display); }
.subnet-field-input {
  flex: 1; padding: 10px 12px; background: var(--bg); border: 1.5px solid var(--border-mid);
  border-radius: var(--radius-sm); font-family: var(--font-mono); font-size: 0.9rem;
  color: var(--text); outline: none; transition: border-color var(--transition);
}
.subnet-field-input:focus { border-color: var(--accent); }
.subnet-field-input.correct { border-color: var(--success); background: var(--success-dim); }
.subnet-field-input.wrong   { border-color: var(--error); background: var(--error-dim); }

/* ── Game score/completion ───────────────────────────────────────────── */
.game-score {
  display: flex; align-items: center; justify-content: center; gap: 8px;
  font-family: var(--font-display); font-size: 1rem; font-weight: 700;
  color: var(--text-muted); padding: 8px;
}
.game-score-val { color: var(--accent); font-size: 1.1rem; }

/* ══════════════════════════════════════════════════════════════════════
   DESKTOP LAYOUT  ≥ 768 px
   ══════════════════════════════════════════════════════════════════════ */
@media (min-width: 768px) {
  #app { max-width: 100%; }

  #screen-home.active { flex-direction: row; overflow: hidden; }
  .home-header {
    width: 320px; flex-shrink: 0;
    border-right: 1px solid var(--border); border-bottom: none;
    padding: 40px 32px 32px;
    overflow-y: auto; overflow-x: hidden;
    display: flex; flex-direction: column;
  }
  .home-continue-btn { margin-top: auto; padding-top: 20px; width: 100%; }
  .topic-grid {
    flex: 1; min-height: 0; overflow-y: auto; overflow-x: hidden;
    -webkit-overflow-scrolling: touch;
    display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    align-content: start; padding: 20px 24px; padding-bottom: 32px; gap: 10px;
  }
  .part-label { grid-column: 1 / -1; margin-top: 14px; }

  .screen-header { padding: 18px 44px; }
  .topic-hero { padding: 28px 44px; }
  .activity-list { padding: 20px 44px; max-width: none; }
  .topic-footer { padding: 18px 44px; padding-bottom: max(18px, calc(14px + env(safe-area-inset-bottom))); }

  .activity-step { padding: 10px 44px; }
  .activity-body { padding: 32px 44px; max-width: 860px; margin: 0 auto; width: 100%; box-sizing: border-box; }
  .activity-footer { padding: 16px 44px; padding-bottom: max(16px, calc(12px + env(safe-area-inset-bottom))); }
  .result-footer-bar { max-width: 772px; margin: 0 auto; width: 100%; }
  .activity-question { font-size: 1.12rem; }
  .mc-options { gap: 12px; }
  .mc-option { padding: 16px 20px; font-size: 0.97rem; }
  .tokens-area { padding: 14px 18px; gap: 10px; }
  .result-panel { padding-top: 24px; }
  .result-explanation { font-size: 0.95rem; line-height: 1.7; }
  .topic-complete { padding: 64px 32px; }
  .topic-complete h2 { font-size: 2.4rem; }

  .lesson-header { padding: 18px 44px 0; }
  .lesson-header-row { padding-bottom: 14px; }
  .lesson-body { padding: 32px 44px; max-width: 860px; margin: 0 auto; width: 100%; box-sizing: border-box; }
  .lesson-footer { padding: 16px 44px; padding-bottom: max(16px, calc(12px + env(safe-area-inset-bottom))); max-width: 860px; margin: 0 auto; width: 100%; box-sizing: border-box; }
  .lesson-card { padding: 28px; }
  .lesson-card-title { font-size: 1.4rem; }
  .lesson-card-body { font-size: 1rem; }
}