/* ── Tokens (match root site) ──────────────────────── */
:root {
  --bg: #0a0a0a;
  --text: #f5f5f5;
  --text-muted: #888;
  --accent: #00FF67;
  --card-bg: #111;
  --card-border: #222;
  --input-bg: #181818;
  --input-border: #333;
  --error: #ff4444;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #fff;
    --text: #1a1a1a;
    --text-muted: #666;
    --card-bg: #fafafa;
    --card-border: #e0e0e0;
    --input-bg: #f0f0f0;
    --input-border: #ccc;
    --error: #cc0000;
  }
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  min-height: 100vh;
}

/* ── Header ───────────────────────────────────────── */
.site-header {
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--card-border);
  display: flex;
  align-items: center;
  gap: 1rem;
}

.breadcrumb {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.85rem;
}
.breadcrumb:hover { color: var(--accent); }

.site-header h1 {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--accent);
}

/* ── Main layout ──────────────────────────────────── */
.app-layout {
  display: grid;
  grid-template-columns: 340px 1fr;
  height: calc(100vh - 56px);
}

@media (max-width: 900px) {
  .app-layout {
    grid-template-columns: 1fr;
    height: auto;
  }
}

/* ── Input panel ──────────────────────────────────── */
.input-panel {
  padding: 1rem;
  overflow-y: auto;
  border-right: 1px solid var(--card-border);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

@media (max-width: 900px) {
  .input-panel {
    border-right: none;
    border-bottom: 1px solid var(--card-border);
    max-height: 50vh;
  }
}

.section-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 8px;
  padding: 0.75rem;
  overflow: hidden;
}

.section-card h2 {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

/* ── Form elements ────────────────────────────────── */
.form-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.4rem;
}

.form-row label {
  font-size: 0.8rem;
  min-width: 60px;
  color: var(--text-muted);
}

.form-row input,
.form-row select {
  flex: 1;
  min-width: 0;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 4px;
  color: var(--text);
  padding: 0.35rem 0.5rem;
  font-size: 0.85rem;
  font-family: inherit;
}

.form-row input:focus,
.form-row select:focus {
  outline: none;
  border-color: var(--accent);
}

.form-row input.error {
  border-color: var(--error);
}

.coeff-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.4rem;
}

.coeff-grid .form-row {
  margin-bottom: 0;
}

.coeff-grid .form-row label {
  min-width: 20px;
  flex-shrink: 0;
}

.coeff-grid .form-row input {
  width: 0;
}

/* ── Equation display ─────────────────────────────── */
.equation-display {
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 4px;
  padding: 0.5rem 0.75rem;
  margin-top: 0.4rem;
  font-family: "Cambria Math", "Latin Modern Math", "STIX Two Math", Georgia, serif;
  font-size: 0.9rem;
  text-align: center;
  color: var(--accent);
  line-height: 1.8;
}

.equation-display.hidden { display: none; }

/* ── Checkbox ─────────────────────────────────────── */
.checkbox-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.4rem;
}

.checkbox-row input[type="checkbox"] {
  accent-color: var(--accent);
}

.checkbox-row label {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ── Buttons ──────────────────────────────────────── */
.btn-row {
  display: flex;
  gap: 0.5rem;
}

.btn-calculate {
  flex: 1;
  background: var(--accent);
  color: #000;
  border: none;
  border-radius: 6px;
  padding: 0.6rem 1rem;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
}
.btn-calculate:hover { filter: brightness(1.1); }

.btn-download {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 6px;
  padding: 0.6rem 0.75rem;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
}
.btn-download:hover { background: var(--accent); color: #000; }
.btn-download:disabled { opacity: 0.3; cursor: default; }
.btn-download:disabled:hover { background: transparent; color: var(--accent); }

.btn-reset {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--input-border);
  border-radius: 6px;
  padding: 0.6rem 0.75rem;
  font-size: 0.8rem;
  cursor: pointer;
  font-family: inherit;
}
.btn-reset:hover { color: var(--text); border-color: var(--text-muted); }

/* ── Slider ───────────────────────────────────────── */
.slider-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.slider-row input[type="range"] {
  flex: 1;
  accent-color: var(--accent);
}

.slider-value {
  font-size: 0.8rem;
  color: var(--accent);
  min-width: 50px;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

/* ── Errors ───────────────────────────────────────── */
.error-container {
  background: var(--error);
  color: #fff;
  border-radius: 6px;
  padding: 0.5rem 0.75rem;
  font-size: 0.8rem;
}

.error-container.hidden { display: none; }

.error-msg { margin-bottom: 0.2rem; }
.error-msg:last-child { margin-bottom: 0; }

/* ── Hidden utility ───────────────────────────────── */
.hidden { display: none !important; }

/* ── Chart panel ──────────────────────────────────── */
.chart-panel {
  padding: 0.5rem;
  overflow: hidden;
  min-height: 0;
}

.chart-grid {
  display: grid;
  gap: 0.5rem;
  height: 100%;
}

.chart-grid.batch {
  grid-template-columns: 1fr 1fr;
  grid-template-rows: 1fr 1fr 1fr;
}

.chart-grid.continuous {
  grid-template-columns: 1fr 1fr 1fr;
  grid-template-rows: 1fr;
}

@media (max-width: 900px) {
  .chart-panel { overflow-y: auto; }

  .chart-grid.batch,
  .chart-grid.continuous {
    grid-template-columns: 1fr;
    grid-auto-rows: 250px;
    height: auto;
  }
}

.chart-wrapper {
  position: relative;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 8px;
  padding: 0.5rem;
  min-height: 0;
  overflow: hidden;
}

.chart-btn-bar {
  position: absolute;
  top: 4px;
  right: 4px;
  z-index: 2;
}

.btn-reset-zoom {
  background: var(--input-bg);
  color: var(--text-muted);
  border: 1px solid var(--input-border);
  border-radius: 4px;
  padding: 2px 6px;
  font-size: 0.65rem;
  cursor: pointer;
  font-family: inherit;
}
.btn-reset-zoom:hover { color: var(--text); }