:root {
  color-scheme: dark;
  color: #c9d1d9;
  background: #0d1117;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  min-height: 100%;
  background: #0d1117;
  color: #c9d1d9;
}

body {
  overflow: hidden;
}

#app {
  width: 100vw;
  height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  padding: 10px 18px 8px;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 18px;
  background: linear-gradient(180deg, rgba(13,17,23,0.94), rgba(13,17,23,0.86));
  border-bottom: 1px solid rgba(255,255,255,0.06);
  z-index: 2;
  min-height: 44px;
}

.intro {
  flex: 1 1 0;
  min-width: 220px;
}

header h1 {
  margin: 0;
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

header p {
  margin: 6px 0 0;
  font-size: 0.82rem;
  color: #8b949e;
  line-height: 1.1;
}

#timeline-wrap {
  position: relative;
  flex: 1;
  overflow: auto;
  background: radial-gradient(circle at top left, rgba(97, 140, 255, 0.08), transparent 22%),
              linear-gradient(90deg, transparent 0%, rgba(255,255,255,0.02) 1px, transparent 2px),
              #0d1117;
}

#timeline-svg {
  display: block;
  width: max-content;
  height: 100%;
  min-height: 100%;
}

.tooltip {
  position: absolute;
  top: 0;
  left: 0;
  padding: 10px 12px;
  border-radius: 12px;
  background: rgba(16, 22, 33, 0.94);
  border: 1px solid rgba(255,255,255,0.08);
  color: #f0f6fc;
  font-size: 0.92rem;
  pointer-events: none;
  opacity: 0;
  transform: translate(-50%, -110%);
  transition: opacity 120ms ease, transform 120ms ease;
  white-space: nowrap;
  z-index: 3;
}

.tooltip.visible {
  opacity: 1;
  transform: translate(-50%, -120%);
}

.tooltip strong {
  display: block;
  font-weight: 700;
  margin-bottom: 4px;
}

.controls {
  display: flex;
  flex-direction: column;
  gap: 8px;
  align-items: flex-end;
  justify-content: flex-start;
  padding: 6px 0;
}

.controls button {
  border: 1px solid rgba(148,163,184,0.18);
  background: rgba(255,255,255,0.04);
  color: #c9d1d9;
  padding: 8px 10px;
  border-radius: 10px;
  font-size: 0.85rem;
  font-weight: 600;
  transition: background 120ms ease, border-color 120ms ease, transform 80ms ease;
}

.controls button:active {
  transform: translateY(1px);
}

.controls button:hover,
.controls button:focus-visible {
  background: rgba(255,255,255,0.12);
  border-color: rgba(148,163,184,0.4);
  outline: none;
}

.hint {
  color: #8b949e;
  font-size: 0.82rem;
  margin-top: 4px;
}

#timeline-wrap {
  position: relative;
  flex: 1;
  overflow: auto;
  background: radial-gradient(circle at top left, rgba(97, 140, 255, 0.08), transparent 22%),
              linear-gradient(90deg, transparent 0%, rgba(255,255,255,0.02) 1px, transparent 2px),
              #0d1117;
  overscroll-behavior: contain;
}

/* hide native scrollbars since we support panning with the mouse */
#timeline-wrap {
  -ms-overflow-style: none; /* IE and Edge */
  scrollbar-width: none; /* Firefox */
}

#timeline-wrap::-webkit-scrollbar {
  display: none; /* WebKit browsers */
}

#timeline-svg {
  display: block;
  width: max-content;
  height: 100%;
  min-height: 100%;
  touch-action: none;
}

.year-label {
  fill: #8b949e;
  font-size: 0.85rem;
  text-anchor: middle;
}

.grid-line {
  stroke: rgba(148,163,184,0.12);
  stroke-width: 1;
}

.axis-line {
  stroke: rgba(148,163,184,0.22);
  stroke-width: 1.5;
}

.link-path {
  fill: none;
  stroke: rgba(148,163,184,0.8);
  stroke-width: 1.4;
  opacity: 0.9;
}

.node-text {
  fill: #f8fafc;
  font-size: 0.85rem;
  pointer-events: none;
  font-weight: 600;
}