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

:root {
  --color-primary: #2563eb;
  --color-text: #111;
  --color-text-2: #444;
  --color-text-3: #888;
  --color-bg: #fff;
  --color-surface: #f8f8f8;
  --color-border: #e5e5e5;
  --font-sans: system-ui, -apple-system, sans-serif;
  --font-mono: 'Menlo', 'Monaco', monospace;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  font-size: 15px;
  line-height: 1.6;
}

nav {
  padding: 16px 40px;
  border-bottom: 1px solid var(--color-border);
}

nav > a {
  color: var(--color-text-2);
  text-decoration: none;
  font-size: 14px;
}

nav > a:hover { color: var(--color-primary); }

main {
  max-width: 860px;
  margin: 0 auto;
  padding: 40px 40px 80px;
}

.page-header { margin-bottom: 32px; }
.page-header h1 { font-size: 24px; font-weight: 700; margin-bottom: 8px; }
.page-desc { color: var(--color-text-2); font-size: 15px; }

/* ── Phase tabs ── */

.phase-tabs {
  display: flex;
  gap: 0;
  border: 1px solid var(--color-border);
  border-radius: 10px;
  overflow: hidden;
  margin-bottom: 0;
}

.phase-tab {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 12px 8px;
  background: var(--color-surface);
  border: none;
  border-right: 1px solid var(--color-border);
  cursor: pointer;
  color: var(--color-text-3);
  font-family: var(--font-sans);
  font-size: 13px;
  transition: background 0.15s, color 0.15s;
}

.phase-tab:last-child { border-right: none; }

.phase-tab:hover {
  background: var(--color-border);
  color: var(--color-text);
}

.phase-tab.active {
  background: var(--color-primary);
  color: #fff;
}

.phase-num {
  font-size: 18px;
  font-weight: 700;
  line-height: 1;
}

.phase-label { font-size: 11px; font-weight: 500; }

/* ── Phase desc bar ── */

.phase-desc-bar {
  border: 1px solid var(--color-border);
  border-top: none;
  border-radius: 0 0 8px 8px;
  padding: 12px 16px;
  background: #fffbeb;
  margin-bottom: 24px;
  font-size: 13.5px;
  color: var(--color-text-2);
  line-height: 1.5;
}

.phase-desc { display: none; }
.phase-desc.active { display: block; }

.phase-prompt {
  display: block;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-primary);
  margin-top: 6px;
  background: #fff;
  border: 1px solid #dbeafe;
  border-radius: 4px;
  padding: 5px 10px;
}

/* ── Phase panels ── */

.phase-panels {
  border: 1px solid var(--color-border);
  border-radius: 10px;
  overflow: hidden;
}

.phase-panel { display: none; }
.phase-panel.active { display: block; }

.phase-note {
  font-size: 12.5px;
  color: var(--color-text-3);
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: 10px 16px;
  font-style: italic;
}

/* ── Phase 1: Intentionally raw ── */
.phase-1-content {
  padding: 16px;
  background: #fff;
  font-family: Times, serif;
}

/* ── Phase 2: Styled ── */
.phase-2-content { padding: 0; }

.p2-nav {
  display: flex;
  gap: 20px;
  padding: 14px 20px;
  border-bottom: 1px solid var(--color-border);
}

.p2-nav a {
  color: var(--color-text-2);
  text-decoration: none;
  font-size: 14px;
  font-family: var(--font-sans);
}

.p2-heading {
  font-size: 28px;
  font-weight: 700;
  padding: 24px 20px 16px;
  font-family: var(--font-sans);
  letter-spacing: -0.3px;
}

.p2-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
  padding: 0 20px 20px;
}

.p2-card {
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 16px;
  background: var(--color-surface);
  font-family: var(--font-sans);
}

.p2-cat {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-primary);
  background: #dbeafe;
  padding: 2px 7px;
  border-radius: 4px;
}

.p2-card h2 { font-size: 15px; margin: 10px 0 4px; }
.p2-year { font-size: 12px; color: var(--color-text-3); margin-bottom: 8px; }
.p2-card p:last-child { font-size: 13.5px; color: var(--color-text-2); }

/* ── Phase 3: Interactive ── */
.phase-3-content { padding: 0; }

.p3-nav {
  display: flex;
  gap: 20px;
  padding: 14px 20px;
  border-bottom: 1px solid var(--color-border);
}

.p3-nav a {
  color: var(--color-text-2);
  text-decoration: none;
  font-size: 14px;
  font-family: var(--font-sans);
}

.p3-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 20px 12px;
  flex-wrap: wrap;
  gap: 12px;
}

.p3-heading {
  font-size: 24px;
  font-weight: 700;
  font-family: var(--font-sans);
  letter-spacing: -0.3px;
}

.p3-filters { display: flex; gap: 6px; }

.p3-filter {
  padding: 5px 12px;
  border: 1px solid var(--color-border);
  border-radius: 20px;
  background: var(--color-surface);
  color: var(--color-text-2);
  font-size: 13px;
  cursor: pointer;
  font-family: var(--font-sans);
  transition: background 0.12s, color 0.12s, border-color 0.12s;
}

.p3-filter.active,
.p3-filter:hover {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.p3-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
  padding: 0 20px 20px;
}

.p3-card {
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 16px;
  background: #fff;
  font-family: var(--font-sans);
}

.p3-card[data-hidden="true"] { display: none; }

.p3-cat {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-primary);
  background: #dbeafe;
  padding: 2px 7px;
  border-radius: 4px;
}

.p3-card h2 { font-size: 15px; margin: 10px 0 4px; }
.p3-year { font-size: 12px; color: var(--color-text-3); margin-bottom: 8px; }
.p3-summary { font-size: 13.5px; color: var(--color-text-2); margin-bottom: 10px; }
.p3-detail { margin-top: 10px; padding-top: 10px; border-top: 1px solid var(--color-border); }
.p3-detail p { font-size: 13px; color: var(--color-text-2); margin-bottom: 8px; }
.p3-link { font-size: 13px; color: var(--color-primary); text-decoration: none; }
.p3-link:hover { text-decoration: underline; }

.p3-expand {
  margin-top: 10px;
  background: none;
  border: 1px solid var(--color-border);
  color: var(--color-text-2);
  font-size: 12.5px;
  padding: 4px 10px;
  border-radius: 4px;
  cursor: pointer;
  font-family: var(--font-sans);
  transition: background 0.12s;
}

.p3-expand:hover { background: var(--color-surface); }

/* ── Phase 4: Polished ── */
.phase-4-content { padding: 0; }

.p4-nav {
  display: flex;
  gap: 20px;
  padding: 14px 20px;
  border-bottom: 1px solid var(--color-border);
}

.p4-nav a {
  color: var(--color-text-2);
  text-decoration: none;
  font-size: 14px;
  font-family: var(--font-sans);
  transition: color 0.15s;
}

.p4-nav a:hover { color: var(--color-primary); }

.p4-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 20px 12px;
  flex-wrap: wrap;
  gap: 12px;
}

.p4-heading {
  font-size: 24px;
  font-weight: 700;
  font-family: var(--font-sans);
  letter-spacing: -0.3px;
}

.p4-filters { display: flex; gap: 6px; }

.p4-filter {
  padding: 5px 12px;
  border: 1px solid var(--color-border);
  border-radius: 20px;
  background: var(--color-surface);
  color: var(--color-text-2);
  font-size: 13px;
  cursor: pointer;
  font-family: var(--font-sans);
  transition: background 0.2s, color 0.2s, border-color 0.2s, transform 0.1s;
}

.p4-filter.active,
.p4-filter:hover {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.p4-filter:active { transform: scale(0.96); }

.p4-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
  padding: 0 20px 20px;
}

@keyframes cardIn {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

.p4-card {
  border: 1px solid var(--color-border);
  border-radius: 10px;
  padding: 18px;
  background: #fff;
  font-family: var(--font-sans);
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
  animation: cardIn 0.4s ease both;
  animation-delay: var(--delay, 0s);
}

.p4-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.1);
}

.p4-cat {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-primary);
  background: #dbeafe;
  padding: 2px 7px;
  border-radius: 4px;
}

.p4-card h2 { font-size: 15px; margin: 10px 0 4px; transition: color 0.15s; }
.p4-card:hover h2 { color: var(--color-primary); }
.p4-year { font-size: 12px; color: var(--color-text-3); margin-bottom: 8px; }
.p4-summary { font-size: 13.5px; color: var(--color-text-2); margin-bottom: 12px; }

.p4-link {
  font-size: 13px;
  color: var(--color-primary);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 2px;
  transition: gap 0.15s;
}

.p4-card:hover .p4-link { gap: 5px; }

.p4-card.hidden {
  opacity: 0;
  transform: scale(0.95);
  pointer-events: none;
  transition: opacity 0.2s, transform 0.2s;
}

/* ── Mobile ── */
@media (max-width: 640px) {
  main { padding: 24px 20px 60px; }
  nav { padding: 14px 20px; }
  .phase-tabs { border-radius: 8px; }
  .phase-tab { padding: 10px 4px; }
  .phase-label { display: none; }
}