:root {
  --sidebar: #111827;
  --sidebar-soft: #1f2937;
  --main-bg: #f4f7fb;
  --card: #ffffff;
  --text: #172033;
  --muted: #667085;
  --line: #d9e2ef;
  --accent: #1d6fd8;
  --accent-dark: #1558ac;
  --accent-soft: #e8f1ff;
  --code-bg: #f8fafc;
  --error: #b42318;
  --error-bg: #fff1f0;
  --shadow: 0 18px 45px rgba(17, 24, 39, 0.1);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--main-bg);
  color: var(--text);
  font-family: Georgia, "Times New Roman", serif;
}

button,
input,
a {
  font: inherit;
}

.app-shell {
  display: grid;
  grid-template-columns: 290px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  background:
    linear-gradient(180deg, rgba(29, 111, 216, 0.2), transparent 42%),
    var(--sidebar);
  color: #f9fafb;
  padding: 28px 20px;
}

.brand {
  display: flex;
  gap: 14px;
  align-items: center;
  padding-bottom: 24px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.12);
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 48px;
  height: 48px;
  border-radius: 16px;
  background: var(--accent);
  font-weight: 700;
  font-size: 1.4rem;
}

.brand h1,
.hero-card h2,
.lab-heading h3,
.try-panel h4,
.code-section h4 {
  margin: 0;
}

.brand h1 {
  font-size: 1.2rem;
  line-height: 1.25;
}

.eyebrow {
  margin: 0 0 6px;
  color: var(--accent);
  font-family: "Courier New", monospace;
  font-size: 0.74rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.sidebar .eyebrow {
  color: #93c5fd;
}

.group-list {
  display: grid;
  gap: 8px;
  margin-top: 24px;
}

.group-btn {
  width: 100%;
  border: 1px solid transparent;
  border-radius: 14px;
  background: transparent;
  color: #dbeafe;
  cursor: pointer;
  padding: 13px 14px;
  text-align: left;
  transition: 160ms ease;
}

.group-btn:hover,
.group-btn.active {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(147, 197, 253, 0.45);
  color: #ffffff;
}

.main-content {
  padding: 34px;
}

.hero-card,
.lab-card {
  max-width: 1120px;
  margin: 0 auto 24px;
  border: 1px solid var(--line);
  border-radius: 28px;
  background: var(--card);
  box-shadow: var(--shadow);
}

.hero-card {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  align-items: center;
  padding: 28px;
}

.hero-card h2 {
  font-size: clamp(2rem, 4vw, 3.2rem);
  letter-spacing: -0.05em;
}

.members {
  margin: 10px 0 0;
  color: var(--muted);
  line-height: 1.6;
}

.download-btn,
.run-btn {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  border: 0;
  border-radius: 999px;
  background: var(--accent);
  color: #ffffff;
  cursor: pointer;
  font-weight: 700;
  text-decoration: none;
  white-space: nowrap;
  transition: 160ms ease;
}

.download-btn {
  padding: 13px 18px;
}

.download-btn:hover,
.run-btn:hover {
  background: var(--accent-dark);
  transform: translateY(-1px);
}

.download-btn[aria-disabled="true"],
.run-btn:disabled {
  opacity: 0.55;
  pointer-events: none;
}

.run-btn.loading::before {
  content: "";
  width: 14px;
  height: 14px;
  margin-right: 8px;
  border: 2px solid rgba(255, 255, 255, 0.45);
  border-top-color: #ffffff;
  border-radius: 999px;
  animation: spin 700ms linear infinite;
}

.lab-card {
  overflow: hidden;
}

.tab-row,
.sub-tab-row {
  display: flex;
  gap: 10px;
  overflow-x: auto;
}

.tab-row {
  padding: 18px 22px;
  border-bottom: 1px solid var(--line);
  background: #fbfdff;
}

.sub-tab-row {
  padding: 12px 22px;
  border-bottom: 1px solid var(--line);
  background: var(--accent-soft);
}

.tab-btn,
.sub-tab-btn {
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #ffffff;
  color: var(--muted);
  cursor: pointer;
  padding: 10px 15px;
  white-space: nowrap;
}

.sub-tab-btn {
  padding: 8px 13px;
  font-size: 0.95rem;
}

.tab-btn.active,
.sub-tab-btn.active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent-dark);
  font-weight: 700;
}

.sub-tab-btn.active {
  background: #ffffff;
}

.lab-panel {
  display: grid;
  gap: 24px;
  padding: 28px;
}

.lab-heading {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  align-items: start;
}

.lab-description {
  max-width: 520px;
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

.preview-box {
  display: grid;
  place-items: center;
  min-height: 280px;
  border: 2px dashed #b7c7dc;
  border-radius: 24px;
  background:
    linear-gradient(135deg, rgba(29, 111, 216, 0.06), rgba(17, 24, 39, 0.04)),
    #eef2f7;
  color: #5b677a;
  font-weight: 700;
  text-align: center;
}

.preview-box img {
  width: 100%;
  max-height: 520px;
  object-fit: contain;
  border-radius: 20px;
}

.section-title-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
  margin-bottom: 10px;
}

.file-pill {
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent-dark);
  font-family: "Courier New", monospace;
  font-size: 0.82rem;
  padding: 6px 10px;
}

pre {
  margin: 0;
}

.code-section pre {
  max-height: 540px;
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--code-bg);
}

.code-section code {
  font-family: Consolas, "Courier New", monospace;
  font-size: 0.95rem;
  line-height: 1.6;
}

.try-panel {
  display: grid;
  gap: 12px;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: #fbfdff;
  padding: 22px;
}

.try-panel label {
  font-weight: 700;
}

.input-fields {
  display: grid;
  gap: 14px;
}

.input-field {
  display: grid;
  gap: 7px;
}

.input-help {
  margin: 0;
  color: var(--muted);
}

input,
.output-box {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: #ffffff;
  color: var(--text);
  font-family: Consolas, "Courier New", monospace;
  font-size: 0.95rem;
  line-height: 1.5;
  padding: 14px;
}

input:focus {
  outline: 3px solid rgba(29, 111, 216, 0.18);
  border-color: var(--accent);
}

.run-btn {
  justify-self: start;
  padding: 12px 20px;
}

.output-box {
  min-height: 130px;
  overflow: auto;
  white-space: pre-wrap;
}

.output-box.error {
  border-color: #f2a29b;
  background: var(--error-bg);
  color: var(--error);
}

.empty-state {
  padding: 40px;
  color: var(--muted);
  text-align: center;
}

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

@media (max-width: 840px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    height: auto;
  }

  .group-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .main-content {
    padding: 18px;
  }

  .hero-card,
  .lab-heading {
    flex-direction: column;
  }

  .download-btn {
    width: 100%;
  }
}

@media (max-width: 520px) {
  .group-list {
    grid-template-columns: 1fr;
  }

  .hero-card,
  .lab-panel {
    padding: 20px;
  }

  .preview-box {
    min-height: 220px;
  }
}