@import url("https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;600;700&display=swap");

:root {
  color-scheme: dark;
  --top-bar-height: 44px;
  --shell-border: 1px solid hsl(215 15% 27% / .85);
  --shell-text: hsl(210 40% 98%);
  --shell-muted: hsl(215 16% 62%);
  --display-font: "Space Grotesk", system-ui, sans-serif;
  --workspace-bg: hsl(215 28% 10%);
  --header-bg: var(--workspace-bg);
  --header-border: hsl(215 15% 22%);
  --brand-text: hsl(210 40% 96%);
  --brand-muted: hsl(215 16% 50%);
  --sidebar-bg: hsl(215 20% 16% / .95);
  --sidebar-shadow: 0 8px 32px hsl(215 20% 6% / .55);
  --control-bg: hsl(215 15% 23% / .7);
  --hover-bg: hsl(217 91% 60% / .14);
  --accent: hsl(199 89% 70%);
}

:root[data-theme="light"] {
  color-scheme: light;
  --workspace-bg: #f8fafc;
  --header-bg: #fff;
  --header-border: #d6dde7;
  --brand-text: #172337;
  --brand-muted: #526279;
  --sidebar-bg: #edf2f8;
  --sidebar-shadow: 0 8px 24px hsl(215 25% 25% / .08);
  --shell-border: 1px solid #d6dde7;
  --shell-text: #172337;
  --shell-muted: #526279;
  --control-bg: #f8fafc;
  --hover-bg: #dce7f6;
  --accent: #155ba1;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--workspace-bg);
  color: var(--shell-text);
  font-family: system-ui, sans-serif;
}

.top-bar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  height: var(--top-bar-height);
  padding: 0 12px;
  background: var(--header-bg);
  border-bottom: 1px solid var(--header-border);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-left: 48px;
  color: var(--brand-text);
  font: 13px var(--display-font);
  text-decoration: none;
  white-space: nowrap;
}

.brand strong { letter-spacing: -.01em; }
.brand span { color: var(--brand-muted); }

.theme-toggle {
  display: grid;
  place-items: center;
  width: 32px;
  height: 30px;
  margin-left: auto;
  padding: 0;
  border: var(--shell-border);
  border-radius: 6px;
  background: var(--control-bg);
  color: var(--shell-muted);
  cursor: pointer;
}
.theme-toggle[hidden] { display: none; }
.theme-toggle svg {
  width: 16px;
  height: 16px;
  fill: none;
  stroke: currentColor;
  stroke-width: 1.5;
  stroke-linecap: round;
}
.theme-toggle .moon,
[data-theme="light"] .theme-toggle .sun { display: none; }
[data-theme="light"] .theme-toggle .moon { display: block; }

.workspace { display: flex; min-height: calc(100dvh - var(--top-bar-height)); }

.sidebar {
  position: sticky;
  top: var(--top-bar-height);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  width: 232px;
  height: calc(100dvh - var(--top-bar-height));
  border-right: var(--shell-border);
  background: var(--sidebar-bg);
  box-shadow: var(--sidebar-shadow);
  backdrop-filter: blur(20px);
  overflow: hidden;
}

.sidebar-heading {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  padding: 12px 10px 10px;
  border-bottom: var(--shell-border);
  font: 700 15px var(--display-font);
  letter-spacing: -.02em;
}

.sidebar-toggle {
  display: grid;
  place-items: center;
  width: 26px;
  height: 26px;
  padding: 0;
  border: var(--shell-border);
  border-radius: 6px;
  background: var(--control-bg);
  color: var(--shell-muted);
  cursor: pointer;
}

nav {
  display: grid;
  align-content: start;
  gap: 3px;
  padding: 6px 8px;
  overflow: auto;
}

nav a {
  display: flex;
  align-items: center;
  gap: 7px;
  min-height: 28px;
  padding: 0 6px 0 4px;
  border-radius: 6px;
  color: var(--shell-muted);
  font: 700 10px var(--display-font);
  letter-spacing: .1em;
  text-transform: uppercase;
  text-decoration: none;
  white-space: nowrap;
}

nav svg {
  width: 18px;
  height: 18px;
  fill: none;
  stroke: currentColor;
  stroke-width: 1.5;
  stroke-linecap: round;
  stroke-linejoin: round;
}

nav a:hover,
.sidebar-toggle:hover,
.theme-toggle:hover {
  background: var(--hover-bg);
  color: var(--shell-text);
}

:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.sidebar[data-collapsed] { width: 56px; }
.sidebar[data-collapsed] .sidebar-heading {
  order: 1;
  justify-content: center;
  margin-top: auto;
  padding: 6px 0;
  border: 0;
}
.sidebar[data-collapsed] .sidebar-heading span,
.sidebar[data-collapsed] nav span {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip-path: inset(50%);
}
.sidebar[data-collapsed] .sidebar-toggle {
  width: 40px;
  height: 32px;
  background: transparent;
  border: 0;
}
.sidebar[data-collapsed] .sidebar-toggle svg { transform: rotate(180deg); }
.sidebar[data-collapsed] nav a { justify-content: center; min-height: 36px; padding: 0; }

main { flex: 1; min-width: 0; padding: clamp(16px, 4vw, 48px); }
h1, h2 { margin: 0; font-family: var(--display-font); letter-spacing: -.02em; }
h1 { font-size: clamp(22px, 4vw, 32px); overflow-wrap: anywhere; }
h2 { font-size: 16px; }
p { margin: 6px 0 0; color: var(--shell-muted); font-size: 13px; }
.intro { font-size: 14px; }
section {
  max-width: 640px;
  margin-top: 28px;
  padding-top: 16px;
  border-top: var(--shell-border);
  scroll-margin-top: calc(var(--top-bar-height) + 16px);
}
section:target { border-color: var(--accent); }

@media (max-width: 520px) {
  .sidebar { width: 56px; }
  .sidebar:not([data-collapsed]) { position: fixed; z-index: 20; width: 232px; }
  main { margin-left: 56px; }
  .sidebar[data-collapsed] + main { margin-left: 0; }
}

nav a[aria-current="page"] {
  background: var(--hover-bg);
  color: var(--accent);
}