/* ============================================================
   Theorem v3.1 — Stylesheet
   ============================================================ */
/* ===== THEME VARIABLES ===== */
:root {
  --bg: #0d1117;
  --surface: #161b22;
  --surface2: #1c2333;
  --border: #30363d;
  --text: #e6edf3;
  --text-dim: #8b949e;
  --accent: #58a6ff;
  --accent-glow: rgba(88,166,255,.15);
  --green: #3fb950;
  --green-glow: rgba(63,185,80,.15);
  --orange: #d29922;
  --orange-glow: rgba(210,153,34,.15);
  --red: #f85149;
  --purple: #bc8cff;
  --radius: 12px;
  --sidebar-w: 280px;
  --topbar-h: 56px;
  --left-w: 190px;
}
/* ===== RESET & BASE ===== */
* { margin: 0; padding: 0; box-sizing: border-box; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: 'DM Sans', sans-serif;
  min-height: 100vh;
  overflow: hidden;
}
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(88,166,255,.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(88,166,255,.03) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
  z-index: 0;
}
/* ===== SIDEBAR ===== */
.sidebar {
  position: fixed; top: 0; left: 0; bottom: 0;
  width: var(--sidebar-w);
  background: var(--surface);
  border-right: 1px solid var(--border);
  z-index: 200;
  transform: translateX(-100%);
  transition: transform .3s cubic-bezier(.4,0,.2,1);
  display: flex; flex-direction: column;
  overflow-y: auto;
}
.sidebar.open { transform: translateX(0); }
.sidebar-header {
  padding: 1.5rem 1.2rem 1rem;
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; justify-content: space-between;
}
.sidebar-brand {
  font-family: 'JetBrains Mono', monospace;
  font-size: .95rem; font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.sidebar-close {
  background: none; border: none;
  color: var(--text-dim); font-size: 1.3rem;
  cursor: pointer; padding: .2rem;
  transition: color .2s; line-height: 1;
}
.sidebar-close:hover { color: var(--text); }
.sidebar-section { padding: 1rem .8rem .5rem; }
.sidebar-section-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: .95rem; font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.sidebar-section-label-hidden { display: none; }
.sidebar-footer {
  margin-top: auto;
  padding: 1rem 1.2rem;
  border-top: 1px solid var(--border);
  font-size: .7rem; color: var(--text-dim);
  font-family: 'JetBrains Mono', monospace;
  text-align: center;
}
.sidebar-overlay {
  position: fixed; inset: 0;
  background: rgba(0,0,0,.5);
  z-index: 199; opacity: 0;
  pointer-events: none; transition: opacity .3s;
}
.sidebar-overlay.visible { opacity: 1; pointer-events: auto; }

/* ===== NAV ITEMS ===== */
.nav-item {
  display: flex; align-items: center; gap: .75rem;
  padding: .7rem .8rem; border-radius: 8px;
  cursor: pointer; transition: all .2s;
  margin-bottom: 2px; border: 1px solid transparent;
  user-select: none;
}
.nav-item:hover { background: var(--surface2); }
.nav-item.active { background: var(--accent-glow); border-color: rgba(88,166,255,.2); }
.nav-item.disabled { opacity: .4; cursor: default; pointer-events: none; }
.nav-icon {
  width: 34px; height: 34px;
  display: flex; align-items: center; justify-content: center;
  border-radius: 8px; font-size: 1.1rem; flex-shrink: 0;
}
.nav-item.active .nav-icon { background: var(--accent-glow); }
.nav-label { font-size: .88rem; font-weight: 500; color: var(--text); line-height: 1.2; }
.nav-item.active .nav-label { color: var(--accent); }
.nav-sublabel { font-size: .7rem; color: var(--text-dim); margin-top: 1px; }
.nav-badge {
  margin-left: auto;
  font-family: 'JetBrains Mono', monospace;
  font-size: .6rem; text-transform: uppercase;
  letter-spacing: .5px; padding: .15rem .45rem;
  border-radius: 4px;
  background: var(--orange-glow); color: var(--orange);
  border: 1px solid rgba(210,153,34,.2);
}
/* ===== TOPBAR ===== */
.topbar {
  position: fixed; top: 0; left: 0; right: 0;
  height: var(--topbar-h);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  display: flex; align-items: center;
  padding: 0 1.2rem; gap: 1rem;
}
.menu-btn {
  width: 38px; height: 38px; border-radius: 10px;
  background: var(--surface2); border: 1px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  flex-direction: column; gap: 3.5px;
  cursor: pointer; transition: all .2s;
  padding: 0; flex-shrink: 0;
}
.menu-btn:hover { border-color: var(--accent); background: var(--accent-glow); }
.menu-btn span {
  display: block; width: 16px; height: 1.5px;
  background: var(--text-dim); border-radius: 2px;
  transition: all .3s;
}
.menu-btn:hover span { background: var(--accent); }
.trainer-title-btn {
  flex-shrink: 0;
  margin-right: .25rem;
  transition: transform .15s cubic-bezier(.34,1.56,.64,1);
  cursor: pointer;
  background: none;
  border: none;
  padding: 0;
  text-align: left;
}
.trainer-title-btn:hover { transform: scale(1.05); }
.trainer-title-btn h1 {
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.1rem; font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1.15;
}
.trainer-title-btn p { font-size: .65rem; color: var(--text-dim); line-height: 1.2; }
.topbar-title {
  flex-shrink: 0; margin-right: .25rem;
  transition: transform .15s cubic-bezier(.34,1.56,.64,1);
  cursor: default;
}
.topbar-title:hover { transform: scale(1.05); }
.topbar-title h1 {
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.1rem; font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1.15;
}
.topbar-title p { font-size: .65rem; color: var(--text-dim); line-height: 1.2; }
.topbar-title.trainer-title-btn,
.topbar-title.topbar-title-btn {
  cursor: pointer;
  background: none;
  border: none;
  padding: 0;
  text-align: left;
}

.topbar-title.trainer-title-btn:focus-visible,
.topbar-title.topbar-title-btn:focus-visible {
  outline: 1px solid rgba(88,166,255,.6);
  outline-offset: 6px;
  border-radius: 8px;
}

.trainer-page-dropdown {
  position: fixed;
  min-width: 280px;
  max-width: min(92vw, 360px);
  display: none;
  flex-direction: column;
  gap: .2rem;
  padding: .35rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: 0 14px 34px rgba(0,0,0,.38);
  z-index: 320;
}

.trainer-page-dropdown.open {
  display: flex;
}
.topbar-nav-dropdown {
  min-width: 320px;
  max-width: min(92vw, 380px);
  max-height: min(78vh, 620px);
  overflow-y: auto;
  gap: .25rem;
}

.topbar-nav-dropdown .sidebar-section {
  padding: .15rem;
}

.topbar-nav-dropdown .sidebar-section + .sidebar-section {
  border-top: 1px solid var(--border);
  padding-top: .45rem;
}

.trainer-page-option {
  width: 100%;
  border: 1px solid transparent;
  border-radius: 8px;
  background: transparent;
  color: var(--text);
  font-family: 'DM Sans', sans-serif;
  font-size: .82rem;
  text-align: left;
  padding: .55rem .6rem;
  cursor: pointer;
  transition: background .15s ease, border-color .15s ease, color .15s ease;
}

.trainer-page-option:hover,
.trainer-page-option:focus-visible {
  background: var(--surface2);
  border-color: rgba(88,166,255,.35);
  color: var(--accent);
  outline: none;
}

.trainer-page-option.current {
  cursor: default;
  opacity: .6;
  border-color: rgba(88,166,255,.22);
  background: rgba(88,166,255,.08);
}

.trainer-page-option.current:hover,
.trainer-page-option.current:focus-visible {
  color: var(--text);
  border-color: rgba(88,166,255,.22);
  background: rgba(88,166,255,.08);
}
.trainer-page-option h6 {
  margin: .2rem 0 0;
  font-size: .68rem;
  font-weight: 500;
  color: var(--text-dim);
  line-height: 1.35;
}

.trainer-page-option.hidden-by-filter {
  display: none;
}

.sidebar-section-label.hidden-by-filter {
  display: none;
}

.dash-filters {
  display: flex;
  align-items: center;
  gap: .45rem;
  flex-wrap: wrap;
}

.sidebar-trainer-filters {
  margin: .25rem .2rem .45rem;
  justify-content: flex-start;
}
.dash-filter-btn {
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  padding: 0;
  line-height: 1;
  border-radius: 9px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text-dim);
  font-size: .95rem;
  cursor: pointer;
  transition: all .2s ease;
}
.dash-filter-btn .fi {
  display: block;
  line-height: 1;
  font-size: 16px;
}
.dash-filter-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-glow);
}
.dash-filter-btn.active {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-glow);
  box-shadow: 0 0 0 1px rgba(88,166,255,.25) inset;
}
.dash-filter-btn.hidden-by-filter { display: none; }
.trainer-page-sidebar-section {
  display: flex;
  flex-direction: column;
  gap: .3rem;
}
/* ===== GENERATE BUTTON & CONTROLS ===== */
.btn-gen {
  width: 38px; height: 38px; border-radius: 10px;
  background: linear-gradient(135deg, var(--accent), #1f6feb);
  border: none; color: #fff; font-size: 1.1rem;
  cursor: pointer;
  transition: transform .15s cubic-bezier(.34,1.56,.64,1), box-shadow .2s;
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
}
.btn-gen:hover { transform: scale(1.15); box-shadow: 0 3px 14px rgba(88,166,255,.35); }
.btn-gen:active { transform: scale(.92); }
.topbar-divider { width: 1px; height: 28px; background: var(--border); flex-shrink: 0; }
/* Difficulty slider */
.slider-wrap { display: flex; align-items: center; gap: .6rem; flex-shrink: 0; min-width: 140px; }
.slider-wrap input {
  -webkit-appearance: none; appearance: none; width: 90px; height: 5px;
  border-radius: 3px;
  background: linear-gradient(90deg, var(--green), var(--orange), var(--red));
  outline: none; cursor: pointer; flex-shrink: 0;
}
.slider-wrap input::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--text); border: 2.5px solid var(--bg);
  box-shadow: 0 0 6px rgba(0,0,0,.4); cursor: pointer;
}
.slider-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: .7rem; color: var(--accent); white-space: nowrap;
}
/* Chips */
.chips-row { display: flex; gap: .35rem; flex-wrap: nowrap; overflow: visible; flex-shrink: 1; min-width: 0; }
.chip {
  font-family: 'JetBrains Mono', monospace;
  font-size: .65rem; padding: .3rem .55rem;
  border-radius: 14px; border: 1px solid var(--border);
  background: var(--surface2); color: var(--text-dim);
  cursor: pointer;
  transition: padding .15s cubic-bezier(.34,1.56,.64,1), border-color .15s, background .15s, color .15s;
  user-select: none; white-space: nowrap;
}
.chip.active { border-color: var(--accent); background: var(--accent-glow); color: var(--accent); }
.chip:hover { border-color: var(--accent); padding: .3rem .75rem; }
.chip:active { padding: .3rem .45rem; }
.task-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: .65rem; text-transform: uppercase;
  letter-spacing: 1.5px; color: var(--text-dim);
  white-space: nowrap; flex-shrink: 0;
}
/* Trainer-specific topbar/lp sections */
.tb-section { display: none; align-items: center; gap: 1rem; }
.tb-section.active { display: contents; }
.mode-toggle {
  display: inline-flex;
  align-items: center;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 2px;
  gap: 2px;
}
.mode-toggle-btn {
  border: none;
  border-radius: 999px;
  background: transparent;
  color: var(--text-dim);
  font-family: 'JetBrains Mono', monospace;
  font-size: .65rem;
  letter-spacing: .4px;
  padding: .28rem .6rem;
  cursor: pointer;
  transition: background .15s ease, color .15s ease;
}
.mode-toggle-btn:hover,
.mode-toggle-btn:focus-visible {
  color: var(--accent);
  outline: none;
}
.mode-toggle-btn.active {
  background: var(--accent-glow);
  color: var(--accent);
}
.typed-mode-meta {
  display: none;
  align-items: center;
  gap: .45rem;
  padding: .22rem .55rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface2);
  line-height: 1;
}
.typed-mode-meta-title {
  font-family: 'JetBrains Mono', monospace;
  font-size: .63rem;
  color: var(--accent);
  white-space: nowrap;
}
.typed-mode-meta-scope {
  font-family: 'DM Sans', sans-serif;
  font-size: .72rem;
  color: var(--text-dim);
  white-space: nowrap;
}
.tb-section.typed-mode .random-control {
  display: none !important;
}
.tb-section.typed-mode .typed-mode-meta {
  display: inline-flex;
}
.lp-section.typed-mode {
  display: none !important;
}
/* ===== LEFT PANEL ===== */
.lp-section { display: none; }
.lp-section.active { display: flex; flex-direction: column; gap: .7rem; }
.left-panel {
  position: fixed; top: var(--topbar-h); left: 0; bottom: 0;
  width: var(--left-w); padding: 1rem .8rem;
  z-index: 50;
  display: flex; flex-direction: column; gap: 0;
  overflow-y: auto;
}
.lp-group { display: flex; flex-direction: column; gap: .3rem; }
.lp-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: .6rem; text-transform: uppercase;
  letter-spacing: .8px; color: var(--text-dim);
}
.lp-select {
  font-family: 'DM Sans', sans-serif;
  font-size: .8rem; border: 1px solid var(--border);
  border-radius: 8px; background: var(--surface);
  color: var(--text); padding: .5rem .6rem;
  cursor: pointer; transition: all .2s; width: 100%;
}
.lp-select:hover,
.lp-select:focus { border-color: var(--accent); outline: none; }
/* ===== STAGE (main content area) ===== */
.stage {
  position: fixed; top: var(--topbar-h); left: 0; right: 0; bottom: 0;
  z-index: 1;
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  padding: 2rem 2rem 3rem;
  padding-left: calc(var(--left-w) + 2rem);
  overflow-y: auto;
}
.typed-problem-shell {
  width: min(860px, 100%);
  display: none;
}
.typed-problem-shell.open {
  display: block;
}
.trainer-page.hidden-for-typed {
  display: none !important;
}
.info-chips { display: flex; gap: .6rem; justify-content: center; margin-bottom: 1rem; flex-wrap: wrap; }
.info-chip {
  font-family: 'JetBrains Mono', monospace;
  font-size: .78rem; padding: .35rem .7rem;
  border-radius: 8px; background: var(--surface);
  border: 1px solid var(--border); color: var(--text-dim);
}
.info-chip .katex { font-size: .82rem; }
.fn-display { font-size: 1.8rem; text-align: center; padding: 1rem 0; max-width: 750px; width: 100%; overflow-x: auto; }
.fn-display .katex { font-size: 1.8rem; }
.question-line { font-size: 1.15rem; text-align: center; padding: .6rem 0; margin-top: .5rem; max-width: 750px; width: 100%; overflow-x: auto; }
.question-line .katex { font-size: 1.2rem; }
.worded-question-line {
  max-width: 750px;
  width: fit-content;
  margin: .35rem auto .15rem;
  padding: .45rem .75rem;
  border-left: 3px solid var(--accent);
  background: rgba(88,166,255,.08);
  color: var(--text-dim);
  font-size: .9rem;
  line-height: 1.45;
  text-align: center;
}
/* ===== SOLUTION BOX ===== */
.reveal-row { display: flex; justify-content: center; align-items: center; gap: .65rem; flex-wrap: wrap; margin-top: 1.2rem; margin-bottom: 1rem; }
.btn-reveal {
  background: var(--surface); border: 1px solid var(--border);
  color: var(--text-dim);
  font-family: 'JetBrains Mono', monospace;
  font-size: .8rem; padding: .55rem 1.2rem;
  border-radius: 10px; cursor: pointer; transition: all .2s;
}
.btn-reveal:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-glow); }
.hint-box {
  background: rgba(88,166,255,.08);
  border: 1px solid rgba(88,166,255,.28);
  border-radius: 12px;
  padding: .9rem 1rem;
  max-width: 750px;
  width: 100%;
  margin-bottom: 1rem;
}
.hint-item { display: flex; gap: .65rem; align-items: flex-start; padding: .35rem 0; color: var(--text); }
.hint-badge {
  min-width: 1.2rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: .72rem;
  color: var(--accent);
}
.hint-text { line-height: 1.5; color: var(--text-dim); }
.solution-box {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.4rem;
  max-width: 750px; width: 100%;
  animation: fadeIn .3s ease;
}
.solution-box .katex { font-size: 1rem; }
.sol-header { display: flex; align-items: center; justify-content: space-between; margin-bottom: .8rem; }
.sol-title {
  font-family: 'JetBrains Mono', monospace;
  font-size: .75rem; text-transform: uppercase;
  letter-spacing: 1px; color: var(--text-dim);
}
.toggle-steps {
  display: inline-flex; align-items: center; gap: .5rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: .7rem; color: var(--text-dim);
  cursor: pointer; user-select: none;
}
.toggle-steps:hover { color: var(--accent); }
.toggle-box {
  width: 30px; height: 16px;
  background: var(--border); border-radius: 8px;
  position: relative; transition: background .2s; cursor: pointer;
}
.toggle-box.active { background: var(--accent); }
.toggle-box::after {
  content: ''; position: absolute;
  width: 12px; height: 12px; background: #fff;
  border-radius: 50%; top: 2px; left: 2px;
  transition: transform .2s;
}
.toggle-box.active::after { transform: translateX(14px); }
/* Steps */
.step { display: flex; gap: .7rem; align-items: flex-start; padding: .5rem 0; border-bottom: 1px solid rgba(48,54,61,.4); }
.step:last-child { border-bottom: none; }
.step-num {
  font-family: 'JetBrains Mono', monospace;
  font-size: .65rem; min-width: 22px; height: 22px;
  display: flex; align-items: center; justify-content: center;
  background: var(--accent-glow); color: var(--accent);
  border-radius: 50%; flex-shrink: 0; margin-top: 2px;
}
.step-num.head {
  background: var(--orange-glow); color: var(--orange);
  min-width: 26px; height: 26px;
  font-size: .7rem; font-weight: 700;
}
.step-text { flex: 1; line-height: 1.6; color: var(--text); font-size: .9rem; overflow: hidden; }
.step-text .katex { font-size: .95rem; }
/* Final answer */
.final-answer {
  margin-top: .8rem; padding: .7rem 1rem;
  background: var(--green-glow);
  border: 1px solid rgba(63,185,80,.3);
  border-radius: 8px; text-align: center;
  overflow: hidden; position: relative;
  display: flex; align-items: center; gap: .8rem;
}
.final-answer-content { flex: 1; text-align: center; overflow: hidden; }
.final-answer-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: .65rem; text-transform: uppercase;
  letter-spacing: 1px; color: var(--green);
  margin-bottom: .3rem;
}
.final-answer .katex { font-size: 1.05rem; }
/* Answer buttons (wrong / right) */
.ans-btn {
  width: 32px; height: 32px; border-radius: 50%;
  border: none; font-size: 1rem; cursor: pointer;
  transition: transform .15s cubic-bezier(.34,1.56,.64,1), background .15s;
  display: none; align-items: center; justify-content: center;
  flex-shrink: 0; overflow: hidden;
}
.ans-btn.visible { display: flex; }
.ans-btn.wrong { background: rgba(248,81,73,.15); color: var(--red); }
.ans-btn.wrong:hover { background: rgba(248,81,73,.3); transform: scale(1.15); }
.ans-btn.right { background: rgba(63,185,80,.15); color: var(--green); }
.ans-btn.right:hover { background: rgba(63,185,80,.3); transform: scale(1.15); }
.ans-btn:active { transform: scale(.9); }
.ans-btn.used { opacity: .4; pointer-events: none; }
/* Placeholder & coming soon */
.placeholder { text-align: center; padding: 4rem 1rem; color: var(--text-dim); font-style: italic; }
.placeholder-icon { font-size: 2.5rem; margin-bottom: .5rem; opacity: .3; }
.trainer-page { display: none; }
.trainer-page.active { display: flex; flex-direction: column; align-items: center; width: 100%; }
.coming-soon { text-align: center; padding: 5rem 2rem; }
.coming-soon-icon { font-size: 3.5rem; margin-bottom: 1rem; opacity: .3; }
.coming-soon h2 { font-family: 'JetBrains Mono', monospace; font-size: 1.3rem; color: var(--text); margin-bottom: .5rem; }
.coming-soon p { color: var(--text-dim); font-size: .95rem; }
/* ===== ANIMATIONS ===== */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}
@keyframes slideIn {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}
/* ===== STREAK FIRE WIDGET ===== */
.streak-widget {
  position: fixed; bottom: 1.2rem; left: 1.2rem;
  z-index: 101;
  display: flex; flex-direction: column;
  align-items: center; gap: .2rem;
  user-select: none;
}
.fire-wrap {
  position: relative;
  display: flex; align-items: center; justify-content: center;
  width: 48px; height: 56px;
}
.fire-emoji {
  font-size: 2rem;
  filter: grayscale(1) opacity(.35);
  transition: filter .5s ease, font-size .4s ease;
  line-height: 1;
}
/* Idle flicker */
@keyframes flicker {
  0%   { transform: scale(1)    rotate(0deg);  }
  25%  { transform: scale(1.02) rotate(.3deg);  }
  50%  { transform: scale(.99)  rotate(-.3deg); }
  75%  { transform: scale(1.01) rotate(.2deg);  }
  100% { transform: scale(1)    rotate(0deg);  }
}
.fire-wrap.alive .fire-emoji { animation: flicker 2s ease-in-out infinite; }
/* Fire tiers: colour + size */
.fire-wrap.s1   .fire-emoji { filter: grayscale(0) opacity(.7);  font-size: 2rem;   }
.fire-wrap.s5   .fire-emoji { filter: grayscale(0) opacity(.85) saturate(1.2); font-size: 2.2rem; }
.fire-wrap.s10  .fire-emoji { filter: grayscale(0) opacity(.9)  saturate(1.5) hue-rotate(-10deg);  font-size: 2.5rem; }
.fire-wrap.s20  .fire-emoji { filter: grayscale(0) opacity(.95) saturate(2)   hue-rotate(160deg);  font-size: 2.8rem; }
.fire-wrap.s50  .fire-emoji { filter: grayscale(0) opacity(1)   saturate(2.5) hue-rotate(220deg);  font-size: 3.1rem; }
.fire-wrap.s100 .fire-emoji { filter: grayscale(0) opacity(1)   saturate(1)   brightness(2) hue-rotate(0deg); font-size: 3.5rem; }
/* Streak number colour by tier */
.streak-num {
  font-family: 'JetBrains Mono', monospace;
  font-size: .85rem; font-weight: 700;
  color: var(--text-dim);
  transition: color .4s ease, font-size .4s ease;
}
.fire-wrap.s1   ~ .streak-num { color: var(--orange); }
.fire-wrap.s5   ~ .streak-num { color: #e8690a; }
.fire-wrap.s10  ~ .streak-num { color: var(--red); }
.fire-wrap.s20  ~ .streak-num { color: #58a6ff; }
.fire-wrap.s50  ~ .streak-num { color: var(--purple); }
.fire-wrap.s100 ~ .streak-num { color: #ffd700; }
/* Correct: fire swell */
@keyframes fireSwell {
  0%   { transform: scale(1);    }
  25%  { transform: scale(1.4);  }
  60%  { transform: scale(1.05); }
  100% { transform: scale(1);    }
}
.fire-wrap.anim-grow .fire-emoji { animation: fireSwell .5s ease-in-out; }
/* Correct: old number fades down */
@keyframes numFadeDown {
  0%   { opacity: 1; transform: translateY(0)   scale(1);  }
  100% { opacity: 0; transform: translateY(6px) scale(.8); }
}
/* Correct: new number shoots up */
@keyframes numShootUp {
  0%   { opacity: 0; transform: translateY(0)     scale(.8);  }
  70%  { opacity: 1; transform: translateY(-50px) scale(1.05); }
  100% { opacity: 1; transform: translateY(-50px) scale(1);    }
}
/* Correct: new number drops down with bounce */
@keyframes numDropDown {
  0%   { transform: translateY(-50px) scale(1);    opacity: 1; }
  60%  { transform: translateY(2px)   scale(.95);              }
  80%  { transform: translateY(-1px)  scale(1.02);             }
  100% { transform: translateY(0)     scale(1);    opacity: 1; }
}
/* Milestone glow pulses */
@keyframes milestoneGlow1 {
  0%   { filter: grayscale(0) opacity(.7)  drop-shadow(0 0 0 transparent); }
  50%  { filter: grayscale(0) opacity(1)   drop-shadow(0 0 12px #d29922) drop-shadow(0 0 24px rgba(210,153,34,.4)); }
  100% { filter: grayscale(0) opacity(.7)  drop-shadow(0 0 0 transparent); }
}
@keyframes milestoneGlow5 {
  0%   { filter: grayscale(0) opacity(.85) drop-shadow(0 0 0 transparent); }
  50%  { filter: grayscale(0) opacity(1)   saturate(1.2) drop-shadow(0 0 14px #e8690a) drop-shadow(0 0 28px rgba(232,105,10,.4)); }
  100% { filter: grayscale(0) opacity(.85) saturate(1.2) drop-shadow(0 0 0 transparent); }
}
@keyframes milestoneGlow10 {
  0%   { filter: grayscale(0) opacity(.9)  saturate(1.5) hue-rotate(-10deg) drop-shadow(0 0 0 transparent); }
  50%  { filter: grayscale(0) opacity(1)   saturate(2)   hue-rotate(-10deg) drop-shadow(0 0 16px #f85149) drop-shadow(0 0 32px rgba(248,81,73,.4)); }
  100% { filter: grayscale(0) opacity(.9)  saturate(1.5) hue-rotate(-10deg) drop-shadow(0 0 0 transparent); }
}
@keyframes milestoneGlow20 {
  0%   { filter: grayscale(0) opacity(.95) saturate(2)   hue-rotate(160deg) drop-shadow(0 0 0 transparent); }
  50%  { filter: grayscale(0) opacity(1)   saturate(2.5) hue-rotate(160deg) drop-shadow(0 0 18px #58a6ff) drop-shadow(0 0 36px rgba(88,166,255,.4)); }
  100% { filter: grayscale(0) opacity(.95) saturate(2)   hue-rotate(160deg) drop-shadow(0 0 0 transparent); }
}
@keyframes milestoneGlow50 {
  0%   { filter: grayscale(0) opacity(1)   saturate(2.5) hue-rotate(220deg) drop-shadow(0 0 0 transparent); }
  50%  { filter: grayscale(0) opacity(1)   saturate(3)   hue-rotate(220deg) drop-shadow(0 0 20px #bc8cff) drop-shadow(0 0 40px rgba(188,140,255,.4)); }
  100% { filter: grayscale(0) opacity(1)   saturate(2.5) hue-rotate(220deg) drop-shadow(0 0 0 transparent); }
}
@keyframes milestoneGlow100 {
  0%   { filter: grayscale(0) opacity(1) brightness(2)   drop-shadow(0 0 0 transparent); }
  50%  { filter: grayscale(0) opacity(1) brightness(2.5) drop-shadow(0 0 24px #ffd700) drop-shadow(0 0 48px rgba(255,215,0,.5)); }
  100% { filter: grayscale(0) opacity(1) brightness(2)   drop-shadow(0 0 0 transparent); }
}
.fire-wrap.milestone.s1   .fire-emoji { animation: milestoneGlow1   .8s ease !important; }
.fire-wrap.milestone.s5   .fire-emoji { animation: milestoneGlow5   .8s ease !important; }
.fire-wrap.milestone.s10  .fire-emoji { animation: milestoneGlow10  .8s ease !important; }
.fire-wrap.milestone.s20  .fire-emoji { animation: milestoneGlow20  .8s ease !important; }
.fire-wrap.milestone.s50  .fire-emoji { animation: milestoneGlow50  .8s ease !important; }
.fire-wrap.milestone.s100 .fire-emoji { animation: milestoneGlow100 .8s ease !important; }
/* Incorrect: shake */
@keyframes fireShake {
  0%   { transform: translate(0,0)     rotate(0);     }
  8%   { transform: translate(-4px,0)  rotate(-3deg); }
  16%  { transform: translate(4px,0)   rotate(3deg);  }
  24%  { transform: translate(-3px,0)  rotate(-2deg); }
  32%  { transform: translate(3px,0)   rotate(2deg);  }
  40%  { transform: translate(-2px,0)  rotate(-1deg); }
  50%  { transform: translate(2px,0)   rotate(1deg);  }
  60%  { transform: translate(-1px,0);                 }
  75%  { transform: translate(1px,0);                  }
  100% { transform: translate(0,0)     rotate(0);     }
}
/* Incorrect: extinguish */
@keyframes fireExtinguish {
  0%   { transform: scale(1);   filter: grayscale(0);                }
  30%  { transform: scale(.5);  filter: grayscale(.4);               }
  60%  { transform: scale(.3);  filter: grayscale(.8) opacity(.25);  }
  100% { transform: scale(1);   filter: grayscale(1)  opacity(.35);  }
}
.fire-wrap.anim-shake .fire-emoji { animation: fireShake .5s ease-out, fireExtinguish .9s ease .15s forwards; }
/* Smoke puff */
@keyframes smokePuff {
  0%   { opacity: .5; transform: translateY(0)     scale(.4); }
  40%  { opacity: .3; transform: translateY(-18px) scale(1);   }
  100% { opacity: 0;  transform: translateY(-35px) scale(1.3); }
}
.smoke {
  position: absolute; top: -8px; left: 0;
  width: 100%; text-align: center;
  font-size: 1.2rem; pointer-events: none; opacity: 0;
}
.smoke.puff { animation: smokePuff .7s ease-out forwards; }
/* Flying number */
.flying-num {
  position: absolute; bottom: 100%; left: 0;
  width: 100%; text-align: center;
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700; pointer-events: none;
  z-index: 5; opacity: 0;
}
.flying-num.shoot-up  { animation: numShootUp  .35s ease-out forwards; }
.flying-num.drop-down { animation: numDropDown .3s  ease-out forwards; }
.streak-num.fade-out  { animation: numFadeDown .25s ease     forwards; }
.streak-num.counting  { transition: none; }
/* ===== CALCULATOR ===== */
.calc-btn {
  position: fixed; top: calc(var(--topbar-h) + .8rem); right: .8rem;
  z-index: 101; width: 42px; height: 42px;
  border-radius: 10px; background: transparent; border: none;
  color: var(--text-dim); cursor: pointer;
  transition: transform .15s cubic-bezier(.34,1.56,.64,1), color .2s;
  display: flex; align-items: center; justify-content: center;
}
.calc-btn:hover  { color: var(--accent); transform: scale(1.2); }
.calc-btn:active { transform: scale(.9); }
.calc-btn.active { color: var(--accent); }
.calc-icon {
  display: grid; grid-template-columns: 1fr 1fr;
  gap: 2px;
  font-family: 'JetBrains Mono', monospace;
  font-size: .75rem; line-height: 1;
  width: 24px; height: 24px;
}
.calc-icon span { display: flex; align-items: center; justify-content: center; }
.calc-panel {
  position: fixed; top: calc(var(--topbar-h) + 3.5rem); right: .8rem;
  z-index: 150; width: 280px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 8px 32px rgba(0,0,0,.5);
  display: none; flex-direction: column;
  overflow: hidden; animation: fadeIn .2s ease;
}
.calc-panel.open { display: flex; }
.calc-display {
  background: var(--bg); padding: .8rem 1rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.1rem; color: var(--text);
  text-align: right; min-height: 2.8rem;
  display: flex; flex-direction: column; justify-content: center;
  border-bottom: 1px solid var(--border);
  word-break: break-all;
}
.calc-display .calc-expr { font-size: .65rem; color: var(--text-dim); min-height: .9rem; }
.calc-grid {
  display: grid; grid-template-columns: repeat(5,1fr);
  gap: 1px; padding: 4px; background: var(--bg);
}
.calc-key {
  background: var(--surface2); border: none;
  color: var(--text);
  font-family: 'JetBrains Mono', monospace;
  font-size: .78rem; padding: .55rem 0;
  cursor: pointer;
  transition: transform .15s cubic-bezier(.34,1.56,.64,1), background .12s, color .12s;
  border-radius: 4px;
}
.calc-key:hover   { background: var(--accent-glow); color: var(--accent); transform: scale(1.12); }
.calc-key:active  { transform: scale(.95); }
.calc-key.op      { color: var(--accent); }
.calc-key.fn      { color: var(--orange); font-size: .7rem; }
.calc-key.eq      { background: var(--accent); color: #fff; }
.calc-key.eq:hover { background: #1f6feb; }
.calc-key.clear   { color: var(--red); }
.calc-key.wide    { grid-column: span 2; }
/* ===== SETTINGS ===== */
.settings-btn {
  position: fixed; bottom: 1.2rem; right: 1.2rem;
  z-index: 101; width: 42px; height: 42px;
  border-radius: 50%; background: transparent; border: none;
  color: var(--text-dim); font-size: 1.3rem;
  cursor: pointer;
  transition: transform .4s cubic-bezier(.34,1.56,.64,1), color .2s;
  display: flex; align-items: center; justify-content: center;
}
.settings-btn:hover  { color: var(--accent); transform: rotate(60deg) scale(1.1); }
.settings-btn.active { color: var(--accent); transform: rotate(90deg); }
.settings-overlay {
  position: fixed; inset: 0;
  background: rgba(0,0,0,.5);
  z-index: 300; opacity: 0; pointer-events: none;
  transition: opacity .25s ease;
  display: flex; align-items: center; justify-content: center;
}
.settings-overlay.open { opacity: 1; pointer-events: auto; }
.settings-modal {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 16px; width: 420px;
  max-width: 90vw; max-height: 80vh;
  overflow-y: auto;
  box-shadow: 0 16px 64px rgba(0,0,0,.6);
  transform: scale(.92) translateY(10px); opacity: 0;
  transition: transform .3s ease, opacity .3s ease;
}
.settings-overlay.open .settings-modal { transform: scale(1) translateY(0); opacity: 1; }
.settings-header {
  padding: 1.2rem 1.5rem;
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; justify-content: space-between;
}
.settings-header h2 {
  font-family: 'JetBrains Mono', monospace;
  font-size: 1rem; font-weight: 700;
  color: var(--text); display: flex; align-items: center; gap: .5rem;
}
.settings-close {
  background: none; border: none;
  color: var(--text-dim); font-size: 1.2rem;
  cursor: pointer; padding: .2rem;
  transition: color .2s, transform .15s cubic-bezier(.34,1.56,.64,1);
  line-height: 1;
}
.settings-close:hover { color: var(--text); transform: scale(1.15); }
.settings-body { padding: 1.2rem 1.5rem; display: flex; flex-direction: column; gap: 1.4rem; }
.setting-group { display: flex; flex-direction: column; gap: .5rem; }
.setting-row { display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
.setting-label { font-family: 'DM Sans', sans-serif; font-size: .9rem; color: var(--text); }
.setting-label-wrap { display: inline-flex; align-items: center; gap: .45rem; }
.setting-tag-soon {
  font-family: ''JetBrains Mono'', monospace;
  font-size: .58rem;
  text-transform: uppercase;
  letter-spacing: .9px;
  padding: .15rem .38rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: rgba(148,163,184,.15);
  color: var(--text-dim);
}
.setting-desc { font-size: .72rem; color: var(--text-dim); line-height: 1.4; }
/* Toggle switch */
.toggle-switch {
  width: 40px; height: 22px;
  background: var(--border); border-radius: 11px;
  position: relative; cursor: pointer;
  transition: background .25s ease; flex-shrink: 0;
}
.toggle-switch.on { background: var(--accent); }
.toggle-switch::after {
  content: ''; position: absolute;
  width: 18px; height: 18px; background: #fff;
  border-radius: 50%; top: 2px; left: 2px;
  transition: transform .25s ease;
}
.toggle-switch.on::after { transform: translateX(18px); }
.toggle-switch.disabled {
  opacity: .5;
  cursor: not-allowed;
  pointer-events: none;
  filter: grayscale(.25);
}
/* Timer display */
.timer-display {
  position: fixed;
  top: calc(var(--topbar-h) + .8rem);
  left: calc(var(--left-w) + (100vw - var(--left-w)) / 2);
  transform: translateX(-50%);
  z-index: 101;
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.1rem; color: var(--text-dim);
  background: var(--surface); border: 1px solid var(--border);
  padding: .3rem .8rem; border-radius: 8px;
  display: none; align-items: center; gap: .5rem;
  transition: color .3s;
}
.timer-display.visible { display: flex; }
.timer-display.warn    { color: var(--orange); }
.timer-display.danger  { color: var(--red); }
/* Timer duration selector */
.timer-options { display: flex; gap: .4rem; flex-wrap: wrap; }
.timer-opt {
  font-family: 'JetBrains Mono', monospace;
  font-size: .7rem; padding: .25rem .5rem;
  border-radius: 8px; border: 1px solid var(--border);
  background: var(--surface2); color: var(--text-dim);
  cursor: pointer; transition: all .15s;
}
.timer-opt.active { border-color: var(--accent); background: var(--accent-glow); color: var(--accent); }
.timer-opt:hover  { border-color: var(--accent); }
.timer-custom {
  font-family: 'JetBrains Mono', monospace;
  font-size: .72rem; width: 55px; padding: .25rem .4rem;
  border-radius: 8px; border: 1px solid var(--border);
  background: var(--surface2); color: var(--text);
  outline: none; transition: border-color .15s;
  appearance: textfield;
  -moz-appearance: textfield;
}
.timer-custom::-webkit-outer-spin-button,
.timer-custom::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.timer-custom:focus { border-color: var(--accent); }
.btn-skip { opacity: .9; border-color: var(--orange); color: var(--orange); display: none; }
.exam-entry-btn,.exam-start-btn {
  border: 1px solid var(--border); background: var(--surface2); color: var(--text);
  border-radius: 10px; padding: .45rem .75rem; cursor: pointer;
  font-family: 'JetBrains Mono', monospace; font-size: .72rem;
}
.exam-start-btn { border-color: var(--accent); color: var(--accent); }
.exam-grid { display: grid; grid-template-columns: repeat(auto-fit,minmax(170px,1fr)); gap: .7rem; }
.exam-grid label { display: flex; flex-direction: column; gap: .35rem; font-size: .78rem; color: var(--text-dim); }
.exam-config { margin-top: .75rem; display: flex; flex-direction: column; gap: .9rem; }
.exam-task-mix {
  display: flex;
  flex-wrap: wrap;
  gap: .65rem 1.1rem;
  padding: .35rem 0 .15rem;
}
.exam-task-item {
  font-size: .74rem;
  color: var(--text-dim);
  display: inline-flex;
  align-items: center;
  gap: .45rem;
  line-height: 1.2;
}
.exam-task-item input { transform: translateY(-.5px); }
.exam-start-btn { margin-top: .2rem; align-self: flex-start; }
.exam-summary-overlay { position: fixed; inset: 0; background: rgba(0,0,0,.6); z-index: 350; display: none; align-items: center; justify-content: center; }
.exam-summary-overlay.open { display: flex; }
.exam-summary-card { width: 420px; max-width: 92vw; background: var(--surface); border: 1px solid var(--border); border-radius: 14px; padding: 1rem 1.1rem; position: relative; }
.exam-summary-close { position: absolute; top: .55rem; left: .65rem; border: none; background: transparent; color: var(--text-dim); font-size: 1rem; cursor: pointer; }
.exam-summary-close:hover { color: var(--text); }
.exam-summary-card h3 { margin: 0 0 .7rem; font-family: 'JetBrains Mono', monospace; }
.exam-summary-card p { margin: .35rem 0; font-size: .82rem; color: var(--text-dim); }
.exam-summary-actions { display: flex; gap: .6rem; margin-top: .9rem; }
/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  :root { --left-w: 0px; --sidebar-w: 260px; }
  .left-panel {
    position: relative; top: auto; left: auto; bottom: auto;
    width: 100%; flex-direction: row; flex-wrap: wrap;
    padding: .8rem 1rem; gap: .5rem;
  }
  .lp-group { flex: 1; min-width: 120px; }
  .stage { margin-left: 0; padding: 1.2rem 1rem; justify-content: center; }
  .topbar { gap: .6rem; padding: 0 .8rem; }
  .slider-wrap input { width: 70px; }
  .fn-display { font-size: 1.3rem; }
  .fn-display .katex { font-size: 1.3rem; }
  .calc-panel { width: 260px; right: .5rem; }
  .settings-modal { width: 95vw; }
}