/* ── Special Relativity Essay — Parchment Theme ── */

@import url('https://fonts.googleapis.com/css2?family=Crimson+Text:ital,wght@0,400;0,600;0,700;1,400;1,600&family=EB+Garamond:ital,wght@0,400..800;1,400..800&display=swap');

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

/* ── Body ── */
body {
  background: #f4ead5;
  background-image:
    radial-gradient(ellipse at 20% 50%, rgba(210,180,140,0.15) 0%, transparent 70%),
    radial-gradient(ellipse at 80% 30%, rgba(180,150,110,0.1) 0%, transparent 60%);
  color: #2c1810;
  font-family: 'Crimson Text', Georgia, 'Times New Roman', serif;
  font-size: 19px;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

/* ── Essay container ── */
.essay {
  max-width: 740px;
  margin: 0 auto;
  padding: 60px 40px 120px;
}

/* ── Header ── */
.essay-header {
  text-align: center;
  margin-bottom: 60px;
  padding-bottom: 40px;
  border-bottom: 1px solid #c4b49a;
}

.essay-header h1 {
  font-family: 'EB Garamond', Georgia, serif;
  font-size: 42px;
  font-weight: 500;
  font-style: italic;
  color: #1a0f08;
  letter-spacing: 0.02em;
  margin-bottom: 12px;
}

.essay-header .subtitle {
  font-family: 'EB Garamond', Georgia, serif;
  font-size: 20px;
  font-style: italic;
  color: #6b5344;
  letter-spacing: 0.03em;
}

/* ── Section headings ── */
.essay-section {
  margin-bottom: 48px;
}

.essay-section h2 {
  font-family: 'EB Garamond', Georgia, serif;
  font-size: 28px;
  font-weight: 500;
  font-style: italic;
  color: #1a0f08;
  margin-bottom: 20px;
  padding-top: 24px;
  border-top: 1px solid #d4c4aa;
}

.essay-section h2:first-child,
#sec-prereqs h2 {
  border-top: none;
  padding-top: 0;
}

/* ── Paragraphs ── */
.essay-section p {
  margin-bottom: 18px;
  text-align: justify;
  hyphens: auto;
}

.essay-section p:last-child {
  margin-bottom: 0;
}

/* ── Emphasis & inline elements ── */
.essay-section em {
  font-style: italic;
  color: #8b2500;
}

.essay-section strong {
  font-weight: 700;
  color: #1a0f08;
}

/* ── Inline math/variables ── */
.var {
  font-family: 'EB Garamond', Georgia, serif;
  font-style: italic;
  color: #8b2500;
}

/* ── Live values (updated by slider) ── */
.live-val {
  font-weight: 700;
  color: #8b2500;
  font-variant-numeric: tabular-nums;
  transition: color 0.2s ease;
}

/* ── Concept definitions ── */
.concept {
  font-weight: 600;
  color: #1a5276;
}

/* ── Visualization container ── */
.viz-container {
  margin: 36px -20px;
  background: #faf3e3;
  border: 1px solid #c4b49a;
  border-radius: 6px;
  box-shadow:
    inset 0 1px 3px rgba(0,0,0,0.04),
    0 2px 8px rgba(0,0,0,0.06);
  overflow: hidden;
}

.viz-container canvas {
  display: block;
  width: 100%;
  cursor: default;
}

/* ── Slider bar ── */
.viz-slider {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 18px;
  border-top: 1px solid #d4c4aa;
  background: #f0e6d0;
  user-select: none;
}

.viz-slider-label {
  font-family: 'Crimson Text', Georgia, serif;
  font-size: 14px;
  font-style: italic;
  color: #6b5344;
  white-space: nowrap;
  min-width: 70px;
}

.viz-range {
  flex: 1;
  -webkit-appearance: none;
  appearance: none;
  height: 4px;
  background: linear-gradient(to right, #c4b49a, #8b7355);
  border-radius: 2px;
  outline: none;
  cursor: pointer;
}

.viz-range::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: #faf3e3;
  border: 2px solid #8b7355;
  box-shadow: 0 1px 3px rgba(0,0,0,0.2);
  cursor: grab;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.viz-range::-webkit-slider-thumb:hover {
  border-color: #2c1810;
  box-shadow: 0 1px 6px rgba(0,0,0,0.3);
}

.viz-range::-webkit-slider-thumb:active {
  cursor: grabbing;
  background: #f4ead5;
}

.viz-range::-moz-range-thumb {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: #faf3e3;
  border: 2px solid #8b7355;
  box-shadow: 0 1px 3px rgba(0,0,0,0.2);
  cursor: grab;
}

.viz-slider-value {
  font-family: 'Crimson Text', Georgia, serif;
  font-size: 14px;
  color: #2c1810;
  font-weight: 600;
  min-width: 48px;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

/* ── Essay images ── */
.essay-figure {
  margin: 32px 0;
  text-align: center;
}

.essay-figure img {
  max-width: 320px;
  width: 100%;
  border-radius: 4px;
  border: 1px solid #c4b49a;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

.essay-figure figcaption {
  margin-top: 10px;
  font-family: 'Crimson Text', Georgia, serif;
  font-size: 14px;
  font-style: italic;
  color: #6b5344;
  line-height: 1.5;
}

/* ── Separator between viz and continuation text ── */
.essay-section .viz-container + p {
  margin-top: 24px;
}

/* ── Blockquote / aside for key insights ── */
.insight {
  margin: 24px 0;
  padding: 16px 24px;
  border-left: 3px solid #8b2500;
  background: rgba(139, 37, 0, 0.04);
  font-style: italic;
  color: #4a2c1a;
}

/* ── Edit mode ── */
.edit-toggle {
  position: fixed;
  top: 16px;
  right: 16px;
  z-index: 1000;
  padding: 6px 14px;
  font-family: 'Crimson Text', Georgia, serif;
  font-size: 14px;
  color: #6b5344;
  background: #faf3e3;
  border: 1px solid #c4b49a;
  border-radius: 4px;
  cursor: pointer;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
  transition: all 0.15s ease;
}

.edit-toggle:hover {
  background: #f4ead5;
  border-color: #8b7355;
  color: #2c1810;
}

.edit-toggle.active {
  background: #2c1810;
  color: #faf3e3;
  border-color: #2c1810;
}

/* Editable blocks in edit mode */
body.editing .essay-block {
  position: relative;
  border-radius: 4px;
  transition: background 0.15s ease;
}

body.editing .essay-block:hover {
  background: rgba(139, 37, 0, 0.025);
}

body.editing .essay-block:focus {
  background: rgba(139, 37, 0, 0.04);
  outline: none;
  box-shadow: inset 3px 0 0 #8b2500;
}

/* Block controls (drag handle + delete button) */
body.editing .essay-block .block-controls {
  position: absolute;
  left: -32px;
  top: 2px;
  display: flex;
  flex-direction: column;
  gap: 2px;
  opacity: 0;
  transition: opacity 0.15s;
  user-select: none;
}

body.editing .essay-block:hover .block-controls {
  opacity: 1;
}

body.editing .essay-block .drag-handle,
body.editing .essay-block .delete-btn {
  width: 20px;
  height: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  color: #b8a89a;
  cursor: pointer;
  border: none;
  background: none;
  padding: 0;
  font-family: inherit;
  transition: color 0.15s;
}

body.editing .essay-block .drag-handle {
  cursor: grab;
  font-size: 14px;
}

body.editing .essay-block .drag-handle:active {
  cursor: grabbing;
  color: #8b2500;
}

body.editing .essay-block .delete-btn:hover {
  color: #c62828;
}

/* Add-block button between blocks */
body.editing .add-block-btn {
  display: block;
  width: 100%;
  padding: 2px 0;
  border: none;
  background: none;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.15s;
  position: relative;
}

body.editing .add-block-btn:hover {
  opacity: 1;
}

body.editing .add-block-btn::before {
  content: '';
  display: block;
  height: 2px;
  background: #8b2500;
  border-radius: 1px;
  opacity: 0.4;
}

body.editing .add-block-btn::after {
  content: '+';
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 18px;
  height: 18px;
  line-height: 16px;
  text-align: center;
  font-size: 14px;
  font-weight: bold;
  color: #faf3e3;
  background: #8b2500;
  border-radius: 50%;
}

/* Drop indicator */
body.editing .drop-indicator {
  height: 3px;
  background: #8b2500;
  border-radius: 2px;
  margin: 2px 0;
  pointer-events: none;
}

/* Dragging state */
body.editing .essay-block.dragging {
  opacity: 0.4;
}

/* Viz containers in edit mode: not text-editable but draggable */
body.editing .viz-container {
  pointer-events: auto;
}

.save-toast {
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 1000;
  padding: 8px 18px;
  font-family: 'Crimson Text', Georgia, serif;
  font-size: 14px;
  color: #faf3e3;
  background: #2c1810;
  border-radius: 4px;
  opacity: 0;
  transition: opacity 0.3s ease;
  pointer-events: none;
}

.save-toast.show {
  opacity: 1;
}

/* ── Responsive ── */
@media (max-width: 800px) {
  .essay {
    padding: 40px 20px 80px;
  }
  .essay-header h1 {
    font-size: 32px;
  }
  .essay-section h2 {
    font-size: 24px;
  }
  body {
    font-size: 17px;
  }
  .viz-container {
    margin-left: -10px;
    margin-right: -10px;
  }
}

@media (max-width: 500px) {
  .essay {
    padding: 24px 14px 60px;
  }
  .essay-header h1 {
    font-size: 26px;
  }
  .viz-container {
    margin-left: -14px;
    margin-right: -14px;
    border-radius: 0;
  }
}