:root {
  --bg: #f5f6f8;
  --panel-bg: #ffffff;
  --text: #1a1d23;
  --text-muted: #6b7280;
  --line: #1e2a4a;
  --accent: #ea580c;
  --accent-bg: #fff2e8;
  --border: #e2e5eb;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14161a;
    --panel-bg: #1c1f26;
    --text: #eef0f3;
    --text-muted: #9aa1ac;
    --line: #c7d0e6;
    --accent: #ff8a3d;
    --accent-bg: #3a2716;
    --border: #2b2f38;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.app-header {
  border-bottom: 1px solid var(--border);
  background: var(--panel-bg);
}

.app-header-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 1rem 1.25rem;
}

.app-header h1 {
  margin: 0;
  font-size: 1.25rem;
}

.layout {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  padding: 1rem;
  max-width: 1400px;
  margin: 0 auto;
}

/* Mobile: controls, then instructions, diagram last. */
.controls-panel { order: 1; }
.instructions-panel { order: 2; }
.diagram-panel { order: 3; }

.panel {
  background: var(--panel-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem 1.25rem 1.25rem;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.04), 0 4px 12px rgba(0, 0, 0, 0.04);
}

.panel h2 {
  margin: 0 0 0.9rem;
  padding-bottom: 0.5rem;
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  border-bottom: 1px solid var(--border);
}

.diagram-wrap {
  position: relative;
  line-height: 0;
}

.lathe-photo {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 6px;
}

.overlay {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.ring {
  position: absolute;
  width: 3.6%;
  aspect-ratio: 1 / 1;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  border: 3px solid #d61f1f;
  box-shadow: 0 0 0 4px rgba(214, 31, 31, 0.28);
  opacity: 0;
  transition: opacity 0.15s ease;
}

.ring.highlight {
  opacity: 1;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  margin-bottom: 0.7rem;
}

.field label {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.field select,
.field input {
  padding: 0.55rem 0.6rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--panel-bg);
  color: var(--text);
  font-size: 1rem;
}

.instructions-output .placeholder {
  color: var(--text-muted);
  margin: 0;
}

.instructions-output ol {
  margin: 0;
  padding-left: 1.25rem;
}

.instructions-output li {
  margin-bottom: 0.5rem;
}

.lever-ref {
  font-weight: 700;
  color: var(--accent);
  text-decoration: underline dotted;
  text-underline-offset: 2px;
  cursor: default;
}

/* Desktop layout: diagram, controls and instructions side by side so
   everything fits within the viewport height without scrolling. */
@media (min-width: 900px) {
  body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
  }

  .layout {
    display: grid;
    grid-template-columns: minmax(260px, 340px) minmax(320px, 1fr) minmax(320px, 460px);
    grid-template-areas: "controls instructions diagram";
    align-items: start;
    gap: 1.25rem;
    width: 100%;
  }

  .diagram-panel { grid-area: diagram; }
  .controls-panel { grid-area: controls; }
  .instructions-panel { grid-area: instructions; }
}