:root {
  color-scheme: light;
  --ink: #172126;
  --muted: #5f6c72;
  --paper: #fbfaf6;
  --panel: #ffffff;
  --line: #dde3e3;
  --teal: #0f766e;
  --teal-soft: #d8f1ed;
  --coral: #d9573f;
  --coral-soft: #ffe2dc;
  --gold: #c98716;
  --gold-soft: #fff1cc;
  --green: #4d7c0f;
  --green-soft: #e4f4c8;
  --blue: #2563a7;
  --blue-soft: #dfefff;
  --shadow: 0 18px 46px rgba(25, 35, 38, 0.12);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    radial-gradient(circle at 14% 12%, rgba(216, 241, 237, 0.78), transparent 28rem),
    radial-gradient(circle at 92% 4%, rgba(255, 226, 220, 0.72), transparent 26rem),
    linear-gradient(135deg, #fbfaf6 0%, #eef7f4 46%, #fff7e4 100%);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

button,
input {
  font: inherit;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem clamp(1rem, 3vw, 2rem);
  border-bottom: 1px solid rgba(23, 33, 38, 0.1);
  background: rgba(251, 250, 246, 0.9);
  backdrop-filter: blur(16px);
}

.eyebrow {
  margin: 0 0 0.1rem;
  color: var(--teal);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 0;
  font-size: clamp(1.45rem, 4vw, 2.5rem);
  line-height: 1.05;
}

.status-strip {
  display: grid;
  min-width: 8rem;
  padding: 0.7rem 0.9rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--panel);
  box-shadow: 0 8px 24px rgba(23, 33, 38, 0.08);
  text-align: right;
}

.status-strip span:first-child {
  font-size: 1.7rem;
  font-weight: 900;
  line-height: 1;
}

.status-strip span:last-child {
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 700;
}

.app-shell {
  display: grid;
  grid-template-columns: minmax(16rem, 22rem) minmax(0, 1fr);
  gap: 1rem;
  width: min(1440px, 100%);
  margin: 0 auto;
  padding: 1rem clamp(1rem, 3vw, 2rem) 2rem;
}

.session-nav,
.workspace {
  min-width: 0;
}

.session-nav {
  position: sticky;
  top: 1rem;
  height: calc(100vh - 2rem);
  overflow: auto;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: rgba(255, 255, 255, 0.78);
  box-shadow: var(--shadow);
}

.nav-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.8rem;
}

.nav-head h2 {
  margin: 0;
  font-size: 1rem;
}

.icon-button {
  display: inline-grid;
  place-items: center;
  width: 2.35rem;
  height: 2.35rem;
  border: 1px solid var(--line);
  border-radius: 0.45rem;
  color: var(--ink);
  background: var(--panel);
  cursor: pointer;
}

.session-list {
  display: grid;
  gap: 0.55rem;
}

.session-tab {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: 0.65rem;
  width: 100%;
  padding: 0.75rem;
  border: 1px solid transparent;
  border-radius: 0.5rem;
  background: rgba(255, 255, 255, 0.72);
  color: var(--ink);
  text-align: left;
  cursor: pointer;
}

.session-tab:hover,
.session-tab.active {
  border-color: rgba(15, 118, 110, 0.34);
  background: var(--teal-soft);
}

.session-index {
  display: inline-grid;
  place-items: center;
  width: 2rem;
  height: 2rem;
  border-radius: 999px;
  color: #fff;
  background: var(--teal);
  font-weight: 900;
}

.session-meta {
  display: block;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 700;
}

.check-dot {
  display: inline-grid;
  place-items: center;
  width: 1.7rem;
  height: 1.7rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--green);
  background: #fff;
  font-weight: 900;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(18rem, 0.95fr);
  gap: 1rem;
  align-items: stretch;
  min-height: 22rem;
  margin-bottom: 1rem;
  overflow: hidden;
  border: 1px solid rgba(23, 33, 38, 0.1);
  border-radius: 0.5rem;
  background: linear-gradient(140deg, rgba(255, 255, 255, 0.94), rgba(216, 241, 237, 0.9));
  box-shadow: var(--shadow);
}

.hero-copy {
  padding: clamp(1.2rem, 3vw, 2.2rem);
  min-width: 0;
}

.hero h2 {
  margin-bottom: 0.8rem;
  font-size: clamp(1.9rem, 3.6vw, 3.1rem);
  line-height: 1;
  overflow-wrap: normal;
  hyphens: auto;
}

.hero p {
  max-width: 62ch;
  color: var(--muted);
  line-height: 1.65;
}

.hero-art {
  min-height: 18rem;
  background:
    linear-gradient(160deg, rgba(15, 118, 110, 0.92), rgba(37, 99, 167, 0.8)),
    #0f766e;
}

.hero-art svg {
  display: block;
  width: 100%;
  height: 100%;
}

.tag-row,
.formula-grid,
.actions,
.trainer-foot,
.quick-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
}

.tag {
  display: inline-flex;
  align-items: center;
  min-height: 2rem;
  padding: 0.35rem 0.65rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.82);
  color: var(--muted);
  font-size: 0.86rem;
  font-weight: 800;
}

.layout-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(18rem, 0.95fr);
  gap: 1rem;
  align-items: start;
}

.panel {
  margin-bottom: 1rem;
  padding: clamp(1rem, 2vw, 1.35rem);
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: rgba(255, 255, 255, 0.86);
  box-shadow: 0 14px 34px rgba(23, 33, 38, 0.08);
}

.panel h3 {
  margin-bottom: 0.8rem;
  font-size: 1.25rem;
}

.timeline {
  display: grid;
  gap: 0.7rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.timeline li {
  display: grid;
  grid-template-columns: 5.4rem minmax(0, 1fr);
  gap: 0.8rem;
  align-items: start;
  padding-bottom: 0.7rem;
  border-bottom: 1px solid var(--line);
}

.timeline li:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.time {
  color: var(--teal);
  font-weight: 900;
}

.formula-grid {
  align-items: stretch;
}

.formula {
  flex: 1 1 12rem;
  padding: 0.85rem;
  border: 1px solid var(--line);
  border-radius: 0.45rem;
  background: var(--paper);
}

.formula strong {
  display: block;
  margin-bottom: 0.35rem;
  color: var(--muted);
  font-size: 0.78rem;
  text-transform: uppercase;
}

.formula code {
  font-size: 1.05rem;
  font-weight: 900;
}

.simulator {
  display: grid;
  gap: 0.9rem;
}

.sim-canvas {
  display: grid;
  place-items: center;
  min-height: 18rem;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background:
    linear-gradient(90deg, rgba(23, 33, 38, 0.04) 1px, transparent 1px),
    linear-gradient(0deg, rgba(23, 33, 38, 0.04) 1px, transparent 1px),
    #fff;
  background-size: 24px 24px;
}

.sim-canvas svg {
  width: min(100%, 34rem);
  height: auto;
}

.controls {
  display: grid;
  gap: 0.75rem;
}

.control-line {
  display: grid;
  grid-template-columns: 7rem minmax(0, 1fr) 4.3rem;
  gap: 0.75rem;
  align-items: center;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--teal);
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.55rem;
}

.result-box {
  padding: 0.8rem;
  border-radius: 0.45rem;
  background: var(--blue-soft);
}

.result-box:nth-child(2n) {
  background: var(--gold-soft);
}

.result-box span {
  display: block;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 800;
}

.result-box strong {
  display: block;
  margin-top: 0.2rem;
  font-size: 1.25rem;
}

.trainer {
  display: grid;
  gap: 0.85rem;
}

.task-visual {
  display: grid;
  place-items: center;
  min-height: 12rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: #fff;
}

.task-visual svg {
  width: min(100%, 28rem);
  height: auto;
}

.task-prompt {
  color: var(--muted);
  line-height: 1.55;
}

.question {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 900;
}

.answer-line {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 0.6rem;
  align-items: center;
}

.answer-line input {
  width: 100%;
  min-height: 2.7rem;
  padding: 0.65rem 0.75rem;
  border: 1px solid var(--line);
  border-radius: 0.45rem;
  background: #fff;
}

.unit {
  color: var(--muted);
  font-weight: 900;
}

.primary,
.secondary {
  min-height: 2.6rem;
  padding: 0.65rem 0.9rem;
  border: 1px solid transparent;
  border-radius: 0.45rem;
  font-weight: 900;
  cursor: pointer;
}

.primary {
  color: #fff;
  background: var(--teal);
}

.secondary {
  color: var(--ink);
  border-color: var(--line);
  background: #fff;
}

.primary:hover,
.secondary:hover,
.icon-button:hover {
  transform: translateY(-1px);
}

.feedback {
  min-height: 3rem;
  padding: 0.75rem;
  border-radius: 0.45rem;
  background: var(--paper);
  color: var(--muted);
  line-height: 1.5;
}

.feedback.good {
  background: var(--green-soft);
  color: #2f4e08;
}

.feedback.near {
  background: var(--gold-soft);
  color: #694506;
}

.feedback.bad {
  background: var(--coral-soft);
  color: #7c2517;
}

.quick-card {
  flex: 1 1 13rem;
  padding: 0.9rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: #fff;
}

.quick-card h4 {
  margin: 0 0 0.4rem;
}

.quick-card p {
  margin: 0;
  color: var(--muted);
  line-height: 1.45;
}

.pulse-ring {
  transform-origin: center;
  animation: pulse 3s ease-in-out infinite;
}

.spin-slow {
  transform-origin: center;
  animation: spin 16s linear infinite;
}

.draw-line {
  stroke-dasharray: 720;
  stroke-dashoffset: 720;
  animation: draw 2.2s ease forwards;
}

@keyframes pulse {
  0%,
  100% {
    transform: scale(0.98);
    opacity: 0.76;
  }
  50% {
    transform: scale(1.04);
    opacity: 1;
  }
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

@keyframes draw {
  to {
    stroke-dashoffset: 0;
  }
}

@media (max-width: 980px) {
  .app-shell,
  .hero,
  .layout-grid {
    grid-template-columns: 1fr;
  }

  .session-nav {
    position: static;
    height: auto;
  }
}

@media (max-width: 640px) {
  .topbar {
    align-items: flex-start;
  }

  .status-strip {
    min-width: 6.8rem;
  }

  .timeline li,
  .control-line,
  .answer-line {
    grid-template-columns: 1fr;
  }

  .result-grid {
    grid-template-columns: 1fr;
  }

  .hero h2 {
    font-size: 2.2rem;
  }
}