:root {
  color-scheme: light;
  --bg: #faf4e8;
  --paper: #fffaf0;
  --ink: #17202a;
  --muted: #6b7280;
  --line: rgba(23, 32, 42, 0.14);
  --line-strong: rgba(23, 32, 42, 0.24);
  --terminal: #10161d;
  --terminal-2: #0b1118;
  --terminal-line: rgba(184, 202, 222, 0.12);
  --terminal-text: #dce8f3;
  --terminal-muted: #7f8c99;
  --request: #e56b4f;
  --assistant: #3b82f6;
  --tool: #10b981;
  --loop: #f59e0b;
  --result: #14b8a6;
  --shadow: 0 28px 90px rgba(27, 34, 43, 0.16);
  --radius: 18px;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

[data-theme="bright"] {
  --terminal: #f8fafc;
  --terminal-2: #eef3f8;
  --terminal-line: rgba(23, 32, 42, 0.13);
  --terminal-text: #152033;
  --terminal-muted: #64748b;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100%;
  background:
    linear-gradient(90deg, rgba(23, 32, 42, 0.045) 1px, transparent 1px),
    linear-gradient(0deg, rgba(23, 32, 42, 0.045) 1px, transparent 1px),
    radial-gradient(circle at 72% 12%, rgba(229, 107, 79, 0.12), transparent 30rem),
    var(--bg);
  background-size: 30px 30px, 30px 30px, auto, auto;
  color: var(--ink);
}

button,
a {
  font: inherit;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: grid;
  grid-template-columns: 260px 1fr auto;
  gap: 20px;
  align-items: center;
  padding: 14px 24px;
  border-bottom: 1px solid var(--line);
  background: rgba(250, 244, 232, 0.82);
  backdrop-filter: blur(18px);
}

.brand,
.topic-nav a {
  color: var(--ink);
  text-decoration: none;
}

.brand {
  font-size: 12px;
  font-weight: 950;
  letter-spacing: 0.17em;
  text-transform: uppercase;
}

.topic-nav {
  display: flex;
  justify-content: center;
  gap: 18px;
}

.topic-nav a {
  color: var(--muted);
  font-size: 13px;
  font-weight: 800;
}

.top-actions {
  display: flex;
  gap: 10px;
}

.icon-btn,
.lane,
.scenario,
.control {
  border: 1px solid var(--line);
  background: rgba(255, 250, 240, 0.76);
  color: var(--ink);
  cursor: pointer;
  transition: transform 170ms ease, border-color 170ms ease, background 170ms ease;
}

.icon-btn {
  width: 38px;
  height: 38px;
  border-radius: 999px;
  font-size: 18px;
}

.page-shell {
  width: min(1500px, calc(100% - 28px));
  margin: 0 auto;
  padding: 18px 0 70px;
}

.intro {
  display: block;
  max-width: 1200px;
  padding: 10px 0 16px;
}

.eyebrow,
.terminal-kicker {
  margin: 0 0 10px;
  color: var(--request);
  font-size: 11px;
  font-weight: 950;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.intro h1 {
  max-width: none;
  margin: 0 0 6px;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(1.18rem, 1.7vw, 1.55rem);
  line-height: 1.18;
  letter-spacing: 0;
}

.intro p:last-child {
  max-width: 1180px;
  margin: 0;
  color: var(--muted);
  font-size: clamp(0.95rem, 1.18vw, 1.08rem);
  line-height: 1.65;
}

.scenario-strip {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin: 0 0 14px;
}

.scenario {
  min-height: 78px;
  padding: 14px 16px;
  border-radius: 12px;
  text-align: left;
  background: rgba(255, 250, 240, 0.68);
}

.scenario span {
  display: block;
  margin-bottom: 6px;
  font-weight: 950;
}

.scenario small {
  color: var(--muted);
  font-size: 12px;
  line-height: 1.35;
}

.scenario.active {
  border-color: rgba(229, 107, 79, 0.56);
  background: rgba(229, 107, 79, 0.09);
}

.scenario.active span {
  color: var(--request);
}

.sim-grid {
  display: grid;
  grid-template-columns: minmax(640px, 1.05fr) minmax(560px, 0.95fr);
  gap: 20px;
  align-items: stretch;
}

.sequence-panel,
.terminal-panel,
.chapter-grid article {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.sequence-panel {
  min-height: 720px;
  background: rgba(255, 250, 240, 0.74);
  overflow: hidden;
}

.lane-head {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  border-bottom: 1px solid var(--line);
}

.lane {
  min-height: 92px;
  padding: 18px;
  border-width: 0 1px 0 0;
  text-align: left;
  background: transparent;
}

.lane:last-child {
  border-right: 0;
}

.lane span {
  display: block;
  margin-bottom: 8px;
  font-weight: 950;
}

.lane small {
  color: var(--muted);
  font-size: 12px;
}

.lane.active span {
  color: var(--request);
}

.sequence-stage {
  height: 720px;
  overflow: auto;
  overscroll-behavior: contain;
}

#sequenceSvg {
  display: block;
  width: 100%;
  min-width: 760px;
  height: 900px;
}

.lane-line {
  stroke: rgba(23, 32, 42, 0.13);
  stroke-width: 2;
}

.lane-title {
  font-size: 13px;
  font-weight: 950;
  letter-spacing: 0.08em;
}

.message-line {
  stroke-width: 2.4;
  marker-end: url(#arrow);
  opacity: 0.38;
}

.message-line.visible {
  opacity: 1;
}

.message-block {
  cursor: pointer;
}

.message-card {
  fill: rgba(255, 250, 240, 0.92);
  stroke-width: 1.4;
  rx: 8;
  filter: drop-shadow(0 14px 18px rgba(23, 32, 42, 0.08));
}

.message-card.active {
  stroke-width: 2.2;
  filter: drop-shadow(0 16px 22px rgba(229, 107, 79, 0.18));
}

.message-block.explaining .message-card {
  animation: explainPulse 900ms ease-in-out infinite;
}

.message-kicker {
  font-size: 9px;
  font-weight: 950;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.message-label {
  fill: var(--ink);
  font-size: 12px;
  font-weight: 900;
}

.terminal-panel {
  position: sticky;
  top: 82px;
  height: calc(100vh - 104px);
  min-height: 720px;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) 250px auto;
  overflow: hidden;
  background: linear-gradient(180deg, var(--terminal) 0%, var(--terminal-2) 100%);
  color: var(--terminal-text);
}

.terminal-chrome {
  display: flex;
  align-items: center;
  gap: 8px;
  height: 46px;
  padding: 0 16px;
  border-bottom: 1px solid var(--terminal-line);
}

.dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
}

.red { background: #ff5f56; }
.yellow { background: #ffbd2e; }
.green { background: #27c93f; }

.terminal-title {
  margin-left: 12px;
  color: var(--terminal-muted);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 12px;
}

.terminal-step {
  margin-left: auto;
  padding: 5px 9px;
  border-radius: 999px;
  background: rgba(229, 107, 79, 0.16);
  color: #f2a188;
  font-size: 11px;
  font-weight: 950;
}

.terminal-log {
  min-height: 0;
  padding: 18px 20px 20px;
  overflow: auto;
  border-bottom: 1px solid var(--terminal-line);
}

.term-entry {
  position: relative;
  margin-bottom: 11px;
  border: 1px solid var(--terminal-line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.025);
  overflow: hidden;
  animation: entryIn 260ms ease both;
}

.term-entry.active {
  border-color: rgba(229, 107, 79, 0.58);
}

.term-head {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 11px 14px;
  color: #8ad7ff;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 13px;
  font-weight: 850;
}

.term-status {
  margin-left: auto;
  color: #58d68d;
  font-size: 10px;
  font-weight: 950;
  letter-spacing: 0.12em;
}

.term-body {
  margin: 0;
  padding: 0 14px 15px;
  color: var(--terminal-text);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 13px;
  line-height: 1.65;
  white-space: pre-wrap;
}

.payload-drawer {
  min-height: 0;
  padding: 16px 18px;
  border-bottom: 1px solid var(--terminal-line);
  overflow: hidden;
}

.payload-head {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: start;
}

.payload-head h2 {
  margin: 0 0 8px;
  font-family: Georgia, "Times New Roman", serif;
  font-size: 1.55rem;
  color: var(--terminal-text);
}

#payloadKind {
  flex: 0 0 auto;
  padding: 6px 8px;
  border-radius: 999px;
  border: 1px solid var(--terminal-line);
  color: #f5c36a;
  font-size: 10px;
  font-weight: 950;
  letter-spacing: 0.12em;
}

#payloadBody {
  height: 88px;
  margin: 0;
  overflow: auto;
  color: #8ef0b2;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 12px;
  line-height: 1.55;
  white-space: pre-wrap;
}

.source-locator {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 10px;
  align-items: center;
  margin-top: 10px;
  padding: 9px 10px;
  border: 1px solid var(--terminal-line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.035);
}

.source-locator span {
  color: #f2a188;
  font-size: 10px;
  font-weight: 950;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.source-locator code {
  min-width: 0;
  overflow: hidden;
  color: #8ad7ff;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 12px;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.teaching-note {
  margin: 9px 0 0;
  color: var(--terminal-muted);
  font-size: 12px;
  line-height: 1.48;
}

.terminal-controls {
  display: grid;
  grid-template-columns: auto 1fr auto auto auto auto;
  gap: 10px;
  align-items: center;
  padding: 14px 16px;
}

#stepLabel {
  color: #f2a188;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 11px;
  font-weight: 950;
}

.step-dots {
  display: flex;
  gap: 8px;
  align-items: center;
  justify-content: center;
  min-width: 0;
}

.step-dot {
  width: 12px;
  height: 12px;
  border: 0;
  border-radius: 50%;
  background: #384253;
  cursor: pointer;
}

.step-dot.done {
  background: #d9795d;
}

.step-dot.active {
  outline: 2px solid #fff2e7;
  outline-offset: 3px;
  background: #ff6f4f;
}

.control {
  min-width: 82px;
  padding: 10px 14px;
  border-color: var(--terminal-line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.055);
  color: var(--terminal-text);
  font-weight: 900;
}

.control.primary {
  border-color: rgba(229, 107, 79, 0.76);
  background: rgba(229, 107, 79, 0.16);
  color: #ffd9ca;
}

.control.active {
  border-color: rgba(245, 158, 11, 0.78);
  background: rgba(245, 158, 11, 0.16);
  color: #ffe5a3;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-top: 22px;
}

.chapter-grid article {
  min-height: 220px;
  padding: 24px;
  background: rgba(255, 250, 240, 0.72);
}

.chapter-grid span {
  color: var(--request);
  font-size: 11px;
  font-weight: 950;
  letter-spacing: 0.14em;
}

.chapter-grid h2 {
  margin: 24px 0 12px;
  font-family: Georgia, "Times New Roman", serif;
  font-size: 2rem;
}

.chapter-grid p {
  margin: 0;
  color: var(--muted);
  line-height: 1.7;
}

button:hover {
  transform: translateY(-2px);
}

@keyframes entryIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes explainPulse {
  0%, 100% {
    filter: drop-shadow(0 12px 16px rgba(229, 107, 79, 0.12));
  }
  50% {
    filter: drop-shadow(0 18px 28px rgba(245, 158, 11, 0.36));
  }
}

@media (max-width: 1200px) {
  .topbar {
    grid-template-columns: 1fr auto;
  }

  .topic-nav {
    display: none;
  }

  .sim-grid,
  .scenario-strip,
  .chapter-grid {
    grid-template-columns: 1fr;
  }

  .terminal-panel {
    position: relative;
    top: auto;
    height: 820px;
  }
}

@media (max-width: 720px) {
  .page-shell {
    width: min(100% - 20px, 1500px);
  }

  .topbar {
    padding: 12px 14px;
  }

  .brand {
    max-width: 220px;
  }

  .intro h1 {
    font-size: clamp(1.45rem, 6vw, 2.1rem);
  }

  .lane-head {
    grid-template-columns: 1fr;
  }

  .lane {
    min-height: 70px;
    border-width: 0 0 1px;
  }

  .sequence-stage {
    height: 620px;
  }

  .terminal-panel {
    height: 820px;
    min-height: 0;
    grid-template-rows: auto minmax(0, 1fr) 235px auto;
  }

  .terminal-controls {
    grid-template-columns: 1fr 1fr 1fr;
  }

  #stepLabel,
  .step-dots {
    grid-column: 1 / -1;
  }
}