/* ─── CSS Variables ──────────────────────────────────────────────────────── */
:root {
  --bg-primary:    #0d1117;
  --bg-secondary:  #161b22;
  --bg-tertiary:   #21262d;
  --border:        #30363d;
  --text-primary:  #e6edf3;
  --text-secondary:#8b949e;
  --accent:        #58a6ff;
  --tension:       #39d353;
  --compression:   #f85149;
  --support:       #e3b341;
  --load-color:    #ff7b72;
  --green-btn:     #238636;
  --green-btn-hov: #2ea043;
  --radius:        8px;
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

/* ─── Reset & Base ───────────────────────────────────────────────────────── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

body {
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  font-size: 14px;
  line-height: 1.6;
  min-height: 100vh;
}

/* ─── Header ─────────────────────────────────────────────────────────────── */
header {
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  padding: 18px 32px;
}

.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

header h1 {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.subtitle {
  color: var(--text-secondary);
  font-size: 0.85rem;
  margin-top: 2px;
}

.badges { display: flex; gap: 8px; flex-wrap: wrap; }

.badge {
  font-size: 0.72rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 20px;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  background: var(--bg-tertiary);
  letter-spacing: 0.03em;
}

/* ─── Main Layout ────────────────────────────────────────────────────────── */
main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 28px 32px;
}

.top-section {
  display: flex;
  gap: 24px;
  align-items: flex-start;
}

/* ─── Canvas ─────────────────────────────────────────────────────────────── */
.canvas-wrapper { flex-shrink: 0; }

#trussCanvas {
  display: block;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-primary);
}

.canvas-controls {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 12px;
  flex-wrap: wrap;
}

#solveBtn {
  padding: 7px 22px;
  font-size: 0.9rem;
  font-weight: 600;
  color: #fff;
  background: var(--green-btn);
  border: 1px solid var(--green-btn-hov);
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
}
#solveBtn:hover  { background: var(--green-btn-hov); }
#solveBtn:active { transform: scale(0.97); }

.btn-secondary {
  padding: 7px 16px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-primary);
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.15s;
}
.btn-secondary:hover { background: #2d333b; }

.info-text {
  color: var(--text-secondary);
  font-size: 0.78rem;
  font-style: italic;
}

/* ─── Sidebar ────────────────────────────────────────────────────────────── */
.sidebar {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-width: 200px;
}

.sidebar-title {
  font-size: 0.95rem;
  font-weight: 700;
  border-bottom: 1px solid var(--border);
  padding-bottom: 8px;
}

.info-block h3 {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 5px;
}

.info-block p {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.7;
  display: flex;
  align-items: center;
  gap: 6px;
}

.tag {
  font-size: 0.65rem;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: 4px;
  letter-spacing: 0.04em;
}
.tag.pin     { background: #1f4068; color: var(--accent); }
.tag.roller  { background: #3d2b00; color: var(--support); }
.tag.free    { background: #1a2b1a; color: var(--tension); }

/* ─── Legend ─────────────────────────────────────────────────────────────── */
.legend h3 {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 7px;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 9px;
  font-size: 0.83rem;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.swatch {
  width: 14px;
  height: 14px;
  border-radius: 3px;
  flex-shrink: 0;
}
.swatch.tension      { background: var(--tension); }
.swatch.compression  { background: var(--compression); }
.swatch.original     { background: none; border: 2px dashed #484f58; }
.swatch.load-color   { background: var(--load-color); }
.swatch.support-color{ background: var(--support); }

/* ─── Results Section ────────────────────────────────────────────────────── */
.results-section {
  margin-top: 32px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.placeholder {
  color: var(--text-secondary);
  font-size: 0.9rem;
  text-align: center;
  padding: 36px;
  border: 1px dashed var(--border);
  border-radius: var(--radius);
}

.results-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
}

.results-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.result-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.result-card h3 {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 10px 14px;
  background: var(--bg-tertiary);
  border-bottom: 1px solid var(--border);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--font-mono);
  font-size: 0.82rem;
}

thead th {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
  font-weight: 600;
  padding: 7px 12px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

tbody td {
  padding: 7px 12px;
  border-bottom: 1px solid var(--border);
  color: var(--text-primary);
}

tbody tr:last-child td { border-bottom: none; }
tbody tr:hover td { background: #1c2128; }

.eq-check {
  margin-top: 20px;
  padding: 12px 16px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text-secondary);
}

.eq-check strong { color: var(--tension); }

/* ─── Footer ─────────────────────────────────────────────────────────────── */
footer {
  text-align: center;
  padding: 20px;
  color: var(--text-secondary);
  font-size: 0.8rem;
  border-top: 1px solid var(--border);
  margin-top: 40px;
}

footer a { color: var(--accent); text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* ─── Responsive ─────────────────────────────────────────────────────────── */
@media (max-width: 760px) {
  .top-section { flex-direction: column; }
  main { padding: 20px 16px; }
  header { padding: 16px; }
  .header-inner { flex-direction: column; align-items: flex-start; }
}