@font-face {
  font-family: 'BoldsPixels';
  src: local('BoldsPixels'), local('boldspixels'),
       url('assets/boldspixels.ttf') format('truetype');
  font-style: normal;
  font-weight: 400;
  font-display: swap;
}

@font-face {
  font-family: 'Umbara';
  src: local('Umbara'), local('umbara'),
       url('assets/Umbara.otf') format('opentype');
  font-style: normal;
  font-weight: 400;
  font-display: swap;
}

/* THEME VARIABLES */
:root {
  --bg: #0d1117;
  --surface: #161b22;
  --surface2: #1c2333;
  --border: #30363d;
  --text: #e6edf3;
  --text-dim: #838586;
  --accent: #58a6ff;
  --accent-glow: rgba(88, 166, 255, 0.15);
  --purple: #c08cff;
  --green: #3fb950;
  --green-glow: rgba(63, 185, 80, 0.15);
  --orange: #d29922;
  --orange-glow: rgba(210, 153, 34, 0.15);
  --red: #f85149;
  --dark-green: #238636;
  --sidebar-w: 280px;
  --topbar-h: 56px;
}

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

html,
body {
  background: var(--bg);
  color: var(--text);
  font-family: 'DM Sans', sans-serif;
  min-height: 100vh;
  overflow-x: hidden;
  overflow-y: auto;
  -ms-overflow-style: none;
  scrollbar-width: none;
}

body:not(.index-splash-page) {
  padding-top: var(--topbar-h);
}

html::-webkit-scrollbar,
body::-webkit-scrollbar {
  width: 0;
  height: 0;
  display: none;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(#58a6ff08 1px, transparent 1px),
    linear-gradient(90deg, #58a6ff08 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
  z-index: 0;
}

.page-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 260;
  height: var(--topbar-h);
  display: flex;
  align-items: center;
  gap: 0.9rem;
  padding: 0 1rem;
  border-bottom: 1px solid var(--border);
  background: rgba(13, 17, 23, 0.92);
  backdrop-filter: blur(8px);
}

.sidebar-toggle-btn {
  border: 0;
  background: transparent;
  cursor: pointer;
  padding: 0.3rem 0.15rem;
  display: inline-flex;
  align-items: center;
  flex-shrink: 0;
  line-height: 1;
}

.sidebar {
  position: fixed;
  top: var(--topbar-h);
  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 0.3s cubic-bezier(0.4, 0, 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;
}

.brand::before { /* BRAND TITLE TEXT */
  display: inline-block;
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent);
  content: 'Theorem';
  transform-origin: left center;
  transition: transform .16s cubic-bezier(.34,1.56,.64,1), text-shadow .2s ease;
}

.sidebar-toggle-btn:hover .brand::before {
  transform: scale(1.05);
}

.sidebar-header .brand {
  display: inline-flex;
  align-items: center;
  cursor: default;
}

.sidebar-header .brand:hover::before {
  transform: scale(1.05);
}

.sidebar-close {
  background: none;
  border: none;
  color: var(--text-dim);
  font-size: 1.3rem;
  cursor: pointer;
  padding: 0.2rem;
  transition: color 0.2s;
  line-height: 1;
}

.sidebar-close:hover { color: var(--text); }

.sidebar-section { padding: 1rem 0.8rem 0.5rem; }

.sidebar-section-label {
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--accent);
  margin-top: 0.85rem;
}

.sidebar-section-label:first-child { margin-top: 0; }
.sidebar-section-label-hidden { display: none; }

.sidebar-trainer-filters {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.4rem;
  margin-bottom: 0.7rem;
}

.dash-filter-btn {
  border: 1px solid var(--border);
  background: var(--surface2);
  color: var(--text-dim);
  border-radius: 8px;
  min-height: 34px;
  cursor: pointer;
}

.dash-filter-btn.active,
.dash-filter-btn:hover {
  border-color: var(--accent);
  color: var(--text);
  background: var(--accent-glow);
}

.trainer-page-option {
  width: 100%;
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-dim);
  text-align: left;
  border-radius: 8px;
  padding: 0.48rem 0.56rem;
  margin-top: 0.3rem;
  font: 500 0.9rem 'Umbara', sans-serif;
  cursor: pointer;
}

.trainer-page-option:hover {
  background: var(--surface2);
  color: var(--text);
}

.trainer-page-option.current {
  background: var(--accent-glow);
  border-color: rgba(88, 166, 255, 0.35);
  color: var(--text);
}

.trainer-page-option.hidden-by-filter,
.sidebar-section-label.hidden-by-filter {
  display: none;
}

.sidebar-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 199;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s;
}

.sidebar-overlay.visible {
  opacity: 1;
  pointer-events: auto;
}

@supports ((-webkit-background-clip: text) or (background-clip: text)) {
  .brand::before,
  .sidebar-section-label {
    background: linear-gradient(135deg, var(--accent), var(--purple));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
  }
}

.trainer-page-option.coming-soon {
  color: var(--text-dim);
  background: rgba(255,255,255,0.04);
  border-color: rgba(255,255,255,0.08);
  cursor: not-allowed;
  opacity: 0.65;
  pointer-events: none;
}

.trainer-page-option.coming-soon::after {
  content: 'Soon';
  float: right;
  font-size: 0.72rem;
  padding: 0.12rem 0.45rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  color: var(--text-dim);
  background: rgba(0,0,0,0.25);
}

/* TOP BAR TRAINER TITLE */
.trainer-title { /* TRAINER TITLE TEXT */
  flex: 1 1 auto;
  min-width: 0;
  margin-left: .55rem;
  padding-right: .25rem;
  overflow: hidden;
  transform-origin: left center;
  transition: transform .15s cubic-bezier(.34,1.56,.64,1);
  text-align: left;
}

.trainer-title:hover { transform: scale(1.02); } /* TRAINER TITLE HOVER EFFECT */

.trainer-title p { font-size: .65rem; color: var(--text-dim); line-height: 1.2; } /* TRAINER TITLE PARAGRAPH */

.trainer-title h1 { /* TRAINER TITLE H1 */
  font-family: 'Umbara', '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;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* ===== TYPED PROBLEM UNIT ===== */

.typed-problem-shell {
  position: relative;
  z-index: 1;
  max-width: 760px;
  margin: 2.5rem auto 0;
  padding: 0 1.2rem;
}

.typed-problem-unit {
  width: 100%;
  background: transparent;
  border: none;
  padding: 0;
}

.typed-problem-input-wrap {
  display: flex;
  align-items: center;
  gap: .6rem;
  margin-bottom: .6rem;
}

.typed-problem-input {
  width: 100%;
  min-height: 42px;
  border: none;
  background: transparent;
  color: var(--text);
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: .95rem;
  padding: .65rem 0;
  line-height: 1.35;
  white-space: pre-wrap;
  word-break: break-word;
  overflow-wrap: anywhere;
  outline: none;
}

.typed-problem-input:empty::before {
  content: attr(data-placeholder);
  color: var(--text-dim);
  opacity: .55;
  pointer-events: none;
}

.typed-problem-input:focus { box-shadow: none; }

/* Math tokens */
.math-token {
  display: inline-flex;
  vertical-align: middle;
  margin: 0 .1rem;
}

.math-editable {
  display: inline-block;
  min-width: .9ch;
  min-height: 1.05em;
  outline: none;
  white-space: nowrap;
}

.math-editable:empty::before { content: '\00A0'; }

.frac-token .frac-box {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  min-width: 1.8ch;
}

.frac-token .frac-line {
  width: 100%;
  border-top: 1px solid var(--text-dim);
  margin: .08rem 0;
}

.frac-token .frac-num,
.frac-token .frac-den {
  text-align: center;
  padding: 0 .14rem;
}

.pow-token {
  vertical-align: super;
  margin-left: .03rem;
}

.pow-token .pow-exp { font-size: .78rem; }

.sqrt-token { align-items: flex-start; }

.sqrt-token .sqrt-symbol {
  font-size: 1.12rem;
  line-height: 1;
  margin-right: .03rem;
}

.sqrt-token .sqrt-radicand {
  border-top: 1px solid var(--text-dim);
  padding: .02rem .2rem 0;
  min-width: 1.2ch;
}

/* Solve button */
.typed-problem-solve {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--accent);
  background: var(--accent-glow);
  color: var(--accent);
  font-size: 1rem;
  cursor: pointer;
  transition: transform .12s ease, background .2s ease;
  flex-shrink: 0;
}

.typed-problem-solve:hover {
  transform: scale(1.07);
  background: rgba(88, 166, 255, .22);
}

.typed-problem-solve:active { transform: scale(.93); }

/* Symbol bar */
.typed-problem-symbols {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: .4rem;
  margin-bottom: .7rem;
}

/* Calc-key base (shared with calculator if added later) */
.calc-key {
  background: var(--surface2);
  border: none;
  color: var(--text);
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: .82rem;
  cursor: pointer;
  transition: transform .1s, background .15s;
  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; }

.typed-problem-symbol-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 42px;
  min-width: 40px;
  padding: 0 .62rem;
  line-height: 1;
}

.typed-problem-symbol-btn:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 1px;
}


.sol-header {
  margin-bottom: .35rem;
}

.sol-title {
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--dark-green);
}
.typed-problem-solution { display: none; }
.typed-problem-solution.open { display: block; }

/* Live input preview */
.typed-problem-preview {
  display: none;
  padding: .4rem .1rem .5rem;
  margin-bottom: .35rem;
  border-bottom: none;
  color: var(--text-dim);
  font-size: 1rem;
  overflow-x: auto;
  text-align: center;
}
.typed-problem-preview.active { display: block; }
.typed-problem-preview .katex-display { margin: 0; }

.typed-problem-result {
  margin-top: .75rem;
  margin-bottom: 0;
  padding: .45rem .56rem .5rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: .72rem;
  color: var(--text-dim);
  background: var(--surface2);
}

/* KaTeX answer rendering */
.answer-label {
  display: block;
  opacity: .75;
  font-size: .7rem;
  margin-bottom: .1rem;
}
.answer-math {
  display: block;
  max-width: 100%;
  font-size: 1.05rem;
  overflow: visible;
}
.answer-math .katex-display {
  margin: .15rem 0 0;
  overflow: visible;
}
.answer-math .katex-display > .katex {
  white-space: normal;
  word-break: break-word;
}
.typed-problem-result.pass .answer-math { color: var(--green); }
.typed-problem-result.fail .answer-math { color: var(--red); }
.typed-problem-result.info .answer-math { color: var(--orange); }

.typed-problem-result.pass {
  color: var(--green);
  border-color: rgba(63, 185, 80, .45);
  background: var(--green-glow);
}

.typed-problem-result.fail {
  color: var(--red);
  border-color: rgba(248, 81, 73, .45);
  background: rgba(248, 81, 73, .14);
}

.typed-problem-result.info {
  color: var(--orange);
  border-color: rgba(210, 153, 34, .45);
  background: var(--orange-glow);
}

/* Steps */
.typed-problem-steps {
  display: flex;
  flex-direction: column;
  gap: 0;
  color: var(--text);
  font-size: .84rem;
}

.typed-problem-step { margin: 0; }

.typed-problem-step-text {
  font-family: inherit;
}

.step-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.4em;
  height: 1.4em;
  border-radius: 50%;
  background: var(--surface2);
  border: 1px solid var(--border);
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: .65rem;
  color: var(--text-dim);
  margin-right: .45rem;
  flex-shrink: 0;
}

.step {
  display: flex;
  align-items: baseline;
  padding: .3rem 0;
}


.typed-problem-analysis {
  margin-top: .75rem;
  padding: .55rem .62rem .62rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: rgba(15, 23, 42, .32);
}

.typed-problem-analysis-row {
  display: flex;
  align-items: flex-start;
  gap: .5rem;
  margin-bottom: .42rem;
  font-size: .78rem;
}

.typed-problem-analysis-row:last-of-type {
  margin-bottom: .2rem;
}

.typed-problem-analysis-label {
  min-width: 4.5rem;
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: .72rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: .04em;
}

.typed-problem-analysis-value {
  color: var(--text);
  min-height: 1.1rem;
}

.typed-problem-analysis-value .katex {
  font-size: 1em;
}

.typed-problem-level-curves {
  display: flex;
  flex-direction: column;
  gap: .16rem;
}

.typed-problem-level-line {
  line-height: 1.28;
}

.typed-problem-contour {
  margin-top: .5rem;
}

.typed-problem-contour .typed-problem-analysis-label {
  margin-bottom: .3rem;
}

.typed-problem-contour-canvas {
  width: 100%;
  height: 300px;
  border: 1px solid rgba(132, 160, 196, .45);
  border-radius: 8px;
  background: rgba(7, 18, 36, .95);
  display: block;
}
/* ===== RANDOM GENERATE CONTROLS ===== */

.typed-controls {
  display: flex;
  align-items: center;
  gap: .8rem;
  margin-bottom: 1rem;
}

.random-btn {
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  padding: .45rem .9rem;
  border: 1px solid var(--accent);
  border-radius: 8px;
  background: var(--accent-glow);
  color: var(--accent);
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: .78rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform .12s ease, background .18s ease;
  flex-shrink: 0;
  white-space: nowrap;
}

.random-btn:hover {
  background: rgba(88, 166, 255, .22);
  transform: scale(1.04);
}

.random-btn:active { transform: scale(.95); }

.random-btn-icon {
  font-size: .95rem;
  line-height: 1;
}

.diff-group {
  display: flex;
  align-items: center;
  gap: .5rem;
  flex: 1;
  min-width: 0;
}

.diff-label {
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: 0.90rem;
  color: var(--text-dim);
  white-space: nowrap;
  user-select: none;
}

.diff-value {
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: .90rem;
  color: var(--accent);
  min-width: 1.2ch;
  text-align: center;
}

.diff-slider {
  -webkit-appearance: none;
  appearance: none;
  flex: 1;
  height: 4px;
  border-radius: 2px;
  background: var(--border);
  outline: none;
  cursor: pointer;
  min-width: 80px;
}

.diff-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--bg);
  cursor: pointer;
  transition: transform .1s ease;
}

.diff-slider::-webkit-slider-thumb:hover { transform: scale(1.2); }

.diff-slider::-moz-range-thumb {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--bg);
  cursor: pointer;
}


/* Responsive */
@media (max-width: 768px) {
  .typed-problem-shell {
    padding: 0 .85rem;
    margin-top: 1.5rem;
  }

  .typed-problem-input-wrap {
    align-items: flex-start;
  }

  .typed-controls {
    flex-wrap: wrap;
    gap: .5rem;
  }

  .diff-group { flex: 1 1 100%; }

  .typed-problem-analysis-row {
    flex-direction: column;
    gap: .2rem;
  }

  .typed-problem-analysis-label {
    min-width: 0;
  }

  .typed-problem-contour-canvas {
    height: 240px;
  }
}












/* ===== LEFT EDGE SELECTOR WHEEL ===== */
.edge-wheel-trigger {
  position: fixed;
  top: var(--topbar-h);
  bottom: 0;
  left: 0;
  width: 72px;
  z-index: 244;
}

.edge-wheel-shell {
  --edge-wheel-size: 470px;
  --edge-wheel-left: -322px;
  --edge-wheel-center-x: 146px;
  position: fixed;
  inset: 0;
  z-index: 245;
  pointer-events: none;
}

.edge-wheel {
  position: absolute;
  left: var(--edge-wheel-left);
  top: 50%;
  width: var(--edge-wheel-size);
  height: var(--edge-wheel-size);
  border-radius: 50%;
  transform: translate3d(-62px, -50%, 0) scale(0.975);
  opacity: 0;
  transition: transform 0.32s cubic-bezier(0.22, 1, 0.36, 1), opacity 0.24s ease;
  pointer-events: none;
}

.edge-wheel::before,
.edge-wheel::after {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: 50%;
  pointer-events: none;
}

.edge-wheel::before {
  border: 1px solid rgba(230, 237, 243, 0.14);
  box-shadow:
    inset 0 0 0 1px rgba(88, 166, 255, 0.08),
    0 0 20px rgba(88, 166, 255, 0.06);
}

.edge-wheel::after {
  background:
    radial-gradient(circle at 88% 50%, rgba(88, 166, 255, 0.14) 0, rgba(88, 166, 255, 0) 42%),
    radial-gradient(circle at 80% 50%, rgba(192, 140, 255, 0.12) 0, rgba(192, 140, 255, 0) 48%);
  mix-blend-mode: screen;
}

.edge-wheel-shell.open {
  pointer-events: none;
}

.edge-wheel-shell.open .edge-wheel {
  transform: translate3d(0, -50%, 0) scale(1);
  opacity: 1;
  pointer-events: auto;
}

.edge-wheel-trigger.is-disabled,
.edge-wheel-shell.is-disabled {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.edge-wheel-lockline {
  display: none;
}

.edge-wheel-option {
  position: absolute;
  left: 50%;
  top: 50%;
  border: 0;
  background: transparent;
  color: var(--text-dim);
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.12rem;
  font-family: 'DM Sans', sans-serif;
  font-size: 1rem;
  line-height: 1.05;
  padding: 0.12rem 0.18rem;
  transform: translate(-50%, -50%);
  transform-origin: center center;
  opacity: 0;
  cursor: pointer;
  white-space: nowrap;
  user-select: none;
  transition:
    color 0.16s ease,
    opacity 0.16s ease,
    text-shadow 0.16s ease;
}

.edge-wheel-label {
  display: inline-flex;
  align-items: center;
}

.edge-wheel-subtitle {
  font-family: 'Umbara', 'JetBrains Mono', monospace;
  font-size: 0.58rem;
  letter-spacing: 0.06em;
  line-height: 1;
  text-transform: uppercase;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  opacity: 0.76;
}

.edge-wheel-option.is-ghost {
  pointer-events: none;
}

.edge-wheel-option.is-near {
  color: rgba(230, 237, 243, 0.55);
}

.edge-wheel-option.is-near .edge-wheel-subtitle {
  opacity: 0.52;
}

.edge-wheel-option.is-center {
  color: var(--text);
  text-shadow: 0 0 12px rgba(88, 166, 255, 0.3);
}

.edge-wheel-option.is-center .edge-wheel-subtitle {
  opacity: 0.98;
}

.edge-wheel-option.is-center .edge-wheel-label::after {
  content: '';
  display: inline-block;
  width: 8px;
  height: 8px;
  margin-left: 0.36rem;
  border-radius: 50%;
  vertical-align: middle;
  background: var(--accent);
  box-shadow: 0 0 10px rgba(88, 166, 255, 0.7);
}

.edge-wheel-option.is-hover {
  color: #ffffff;
  text-shadow: 0 0 16px rgba(88, 166, 255, 0.45);
}

.edge-wheel-option.is-hover .edge-wheel-subtitle {
  opacity: 1;
}

.edge-wheel-option:focus-visible {
  outline: none;
  color: #ffffff;
}

@media (max-width: 900px) {
  .edge-wheel-shell {
    --edge-wheel-size: 420px;
    --edge-wheel-left: -292px;
    --edge-wheel-center-x: 126px;
  }

  .edge-wheel-trigger {
    width: 54px;
  }

  .edge-wheel-option {
    font-size: 0.88rem;
  }
}

@media (hover: none), (pointer: coarse) {
  .edge-wheel-trigger,
  .edge-wheel-shell {
    display: none;
  }
}

.edge-wheel-option[aria-selected='true'] {
  border: 0;
  box-shadow: none;
}












.edge-wheel-option .katex {
  font-size: 1em;
  color: currentColor;
  pointer-events: none;
}




.edge-wheel-option .fi {
  font-size: 1.02em;
  line-height: 1;
  color: currentColor;
  pointer-events: none;
}