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

:root {
  --ink: #1a1a2e;
  --paper: #f5f0e8;
  --paper2: #ede8da;
  --grid: #c8bfa8;
  --accent: #c0392b;
  --accent2: #2980b9;
  --accent3: #27ae60;
  --gold: #b7890a;
  --line: #3d3d5c;
}

html, body {
  height: 100%;
  background: var(--paper);
  color: var(--ink);
  font-family: 'Crimson Pro', Georgia, serif;
}

/* GRID PAPER BACKGROUND */
body {
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px),
    linear-gradient(rgba(200,191,168,0.3) 1px, transparent 1px),
    linear-gradient(90deg, rgba(200,191,168,0.3) 1px, transparent 1px);
  background-size: 60px 60px, 60px 60px, 12px 12px, 12px 12px;
  background-position: -1px -1px, -1px -1px, -1px -1px, -1px -1px;
}

header {
  border-bottom: 2px solid var(--ink);
  padding: 20px 40px;
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  background: var(--paper);
  position: relative;
  z-index: 10;
}

header::after {
  content: '';
  position: absolute;
  bottom: -5px;
  left: 0; right: 0;
  height: 1px;
  background: var(--ink);
  opacity: 0.3;
}

.logo {
  font-family: 'Space Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink);
  opacity: 0.6;
}

h1 {
  font-family: 'Crimson Pro', serif;
  font-weight: 300;
  font-size: clamp(28px, 4vw, 48px);
  letter-spacing: -0.02em;
  font-style: italic;
}

h1 span {
  font-style: normal;
  font-weight: 400;
  color: var(--accent);
}

.chapter-label {
  font-family: 'Space Mono', monospace;
  font-size: 10px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--gold);
}

/* MAIN LAYOUT */
main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 40px 40px 80px;
}

.intro {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  margin-bottom: 60px;
  align-items: start;
}

.intro-text h2 {
  font-size: 32px;
  font-weight: 300;
  font-style: italic;
  margin-bottom: 16px;
  line-height: 1.2;
}

.intro-text p {
  font-size: 18px;
  line-height: 1.7;
  color: #2d2d4a;
  opacity: 0.85;
  margin-bottom: 14px;
}

.concept-list {
  list-style: none;
  margin-top: 20px;
}

.concept-list li {
  font-family: 'Space Mono', monospace;
  font-size: 12px;
  padding: 8px 0;
  border-bottom: 1px solid var(--grid);
  display: flex;
  align-items: center;
  gap: 12px;
  cursor: pointer;
  transition: color 0.2s;
  letter-spacing: 0.05em;
}

.concept-list li:hover { color: var(--accent); }

.concept-list li::before {
  content: attr(data-num);
  font-size: 10px;
  color: var(--gold);
  min-width: 20px;
}

.concept-list li.active {
  color: var(--accent);
  font-weight: 700;
}

/* CANVAS SECTION */
.canvas-section {
  background: var(--paper2);
  border: 1px solid var(--ink);
  border-radius: 0;
  padding: 0;
  position: relative;
  box-shadow: 4px 4px 0 var(--ink);
}

.canvas-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 20px;
  border-bottom: 1px solid var(--ink);
  background: var(--ink);
  color: var(--paper);
}

.canvas-toolbar span {
  font-family: 'Space Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.1em;
}

.toolbar-btns { display: flex; gap: 8px; }

.btn-tool {
  background: transparent;
  border: 1px solid rgba(255,255,255,0.3);
  color: var(--paper);
  font-family: 'Space Mono', monospace;
  font-size: 10px;
  padding: 4px 10px;
  cursor: pointer;
  letter-spacing: 0.05em;
  transition: all 0.15s;
}

.btn-tool:hover, .btn-tool.active {
  background: var(--paper);
  color: var(--ink);
}

canvas {
  display: block;
  width: 100%;
}

/* INFO CARDS */
.cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  background: var(--ink);
  border: 1px solid var(--ink);
  margin-top: 60px;
  box-shadow: 4px 4px 0 rgba(26,26,46,0.3);
}

.card {
  background: var(--paper);
  padding: 28px 24px;
  cursor: pointer;
  transition: background 0.2s;
}

.card:hover { background: var(--paper2); }

.card-num {
  font-family: 'Space Mono', monospace;
  font-size: 36px;
  font-weight: 700;
  color: var(--grid);
  line-height: 1;
  margin-bottom: 12px;
}

.card h3 {
  font-size: 18px;
  font-weight: 400;
  margin-bottom: 8px;
  font-style: italic;
}

.card p {
  font-size: 14px;
  line-height: 1.6;
  opacity: 0.7;
}

.card-tag {
  display: inline-block;
  font-family: 'Space Mono', monospace;
  font-size: 9px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  padding: 2px 8px;
  margin-top: 12px;
  border: 1px solid currentColor;
}

.card:nth-child(1) .card-tag { color: var(--accent); }
.card:nth-child(2) .card-tag { color: var(--accent2); }
.card:nth-child(3) .card-tag { color: var(--accent3); }

/* EPURE SECTION */
.epure-section {
  margin-top: 60px;
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: 40px;
  align-items: start;
}

.epure-legend {
  border: 1px solid var(--ink);
  padding: 24px;
  background: var(--paper);
  box-shadow: 3px 3px 0 var(--ink);
}

.epure-legend h3 {
  font-size: 20px;
  font-style: italic;
  margin-bottom: 16px;
  border-bottom: 1px solid var(--grid);
  padding-bottom: 10px;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 0;
  font-size: 15px;
  border-bottom: 1px dotted var(--grid);
}

.legend-dot {
  width: 24px;
  height: 4px;
  flex-shrink: 0;
  border-radius: 2px;
}

/* TOOLTIP */
.tooltip {
  position: absolute;
  background: var(--ink);
  color: var(--paper);
  font-family: 'Space Mono', monospace;
  font-size: 11px;
  padding: 6px 12px;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.2s;
  letter-spacing: 0.05em;
  z-index: 100;
  white-space: nowrap;
}

.tooltip.show { opacity: 1; }

/* FOOTER */
footer {
  border-top: 1px solid var(--ink);
  padding: 20px 40px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: 'Space Mono', monospace;
  font-size: 10px;
  letter-spacing: 0.1em;
  opacity: 0.5;
  background: var(--paper);
}

@media (max-width: 768px) {
  .intro { grid-template-columns: 1fr; gap: 30px; }
  .cards { grid-template-columns: 1fr; }
  .epure-section { grid-template-columns: 1fr; }
  header { padding: 16px 20px; }
  main { padding: 24px 20px 60px; }
}