/*
  Global stylesheet
  - Modern, accessible typography and layout
  - Shared across all pages
*/

/* Reset */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

/* Design tokens */
:root {
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;
  --font-heading: 'Space Grotesk', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;

  /* Modular scale 1.25 */
  --text-xs: 0.8rem;     /* 12.8px */
  --text-sm: 1rem;       /* 16px */
  --text-md: 1.25rem;    /* 20px */
  --text-lg: 1.5625rem;  /* 25px */
  --text-xl: 1.9375rem;  /* 31px */
  --text-2xl: 2.4375rem; /* 39px */

  --line-height-heading: 1.2;
  --line-height-body: 1.55;

  --color-text: hsl(222deg 20% 20%);
  --color-heading: hsl(222deg 22% 12%);
  --color-accent: #6D28D9;
  --color-accent-start: #7C3AED;
  --color-accent-end: #2563EB;
  --color-border: hsl(220deg 18% 88%);
  --color-bg: #FBFBFE;

  --spacing-unit: 1.5rem;
  --max-width: 48rem;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-text: hsl(210deg 14% 92%);
    --color-heading: hsl(210deg 24% 98%);
    --color-accent: #8B5CF6;
    --color-accent-start: #8B5CF6;
    --color-accent-end: #3B82F6;
    --color-border: hsl(220deg 14% 24%);
    --color-bg: #0B1020;
  }
}

html {
  font-size: 16px;
}

body {
  min-height: 100dvh;
  font-family: var(--font-body);
  font-weight: 400;
  line-height: var(--line-height-body);
  color: var(--color-text);
  background: radial-gradient(1200px 600px at 10% -10%, rgba(124, 58, 237, 0.08), transparent 60%),
              radial-gradient(1200px 600px at 90% -10%, rgba(37, 99, 235, 0.08), transparent 60%),
              var(--color-bg);
  display: flex;
  flex-direction: column;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  color: var(--color-heading);
  line-height: var(--line-height-heading);
  margin-bottom: calc(var(--spacing-unit) * 0.5);
}

h1 {
  font-size: var(--text-2xl);
  font-weight: 700;
  margin-bottom: var(--spacing-unit);
}

h2 {
  font-size: var(--text-xl);
  font-weight: 600;
  letter-spacing: -0.015em;
  margin-top: calc(var(--spacing-unit) * 2);
  margin-bottom: var(--spacing-unit);
}

h3 {
  font-size: var(--text-lg);
  font-weight: 600;
  letter-spacing: -0.015em;
}

h4 {
  font-size: var(--text-md);
  font-weight: 600;
  letter-spacing: -0.015em;
}

p {
  margin-bottom: var(--spacing-unit);
  max-width: 70ch;
}

.intro,
.tagline {
  font-size: var(--text-sm);
  margin-bottom: calc(var(--spacing-unit) * 2);
}

/* Navigation */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  border-bottom: 1px solid var(--color-border);
  backdrop-filter: saturate(140%) blur(6px);
  background-color: color-mix(in srgb, var(--color-bg) 85%, transparent);
  margin-bottom: calc(var(--spacing-unit) * 2);
}

.site-nav {
  max-width: var(--max-width);
  margin-inline: auto;
  padding: var(--spacing-unit) 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 2rem;
}

.site-title {
  font-size: clamp(1.75rem, 2vw + 1rem, 2.125rem);
  font-weight: 700;
  line-height: 1.2;
  text-decoration: none;
  color: var(--color-heading);
}

.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

.nav-links a {
  font-weight: 500;
  color: var(--color-text);
  text-decoration: none;
  padding-bottom: 2px;
  background-image: linear-gradient(currentColor, currentColor);
  background-size: 0% 2px;
  background-position: 0 100%;
  background-repeat: no-repeat;
  transition: color 0.2s ease, background-size 0.25s ease;
}

.nav-links a:hover {
  color: var(--color-accent-end);
  background-size: 100% 2px;
}

.nav-links a.active {
  color: var(--color-accent-end);
  background-size: 100% 2px;
}

/* Content links (e.g., in Reading page) */
.page-content a {
  font-weight: 500;
  color: var(--color-text);
  text-decoration: none;
  padding-bottom: 2px;
  background-image: linear-gradient(currentColor, currentColor);
  background-size: 0% 2px;
  background-position: 0 100%;
  background-repeat: no-repeat;
  transition: color 0.2s ease, background-size 0.25s ease;
}

.page-content a:hover {
  color: var(--color-accent-end);
  background-size: 100% 2px;
}

.page-content a:visited {
  color: var(--color-text);
}

@media (max-width: 640px) {
  .site-nav {
    flex-direction: column;
    align-items: stretch;
    gap: 1rem;
  }

  .nav-links {
    overflow-x: auto;
    gap: 1.5rem;
    padding-bottom: 0.5rem;
  }

  .nav-links a {
    white-space: nowrap;
  }
}

/* Layout */
.page-content {
  flex: 1;
  max-width: var(--max-width);
  margin-inline: auto;
  padding: 0 1rem calc(var(--spacing-unit) * 3) 1rem;
}

/* Lists with custom marker */
ul {
  list-style: none;
  padding-inline-start: 1.25rem;
  margin-bottom: var(--spacing-unit);
}

ul li {
  position: relative;
  margin-bottom: calc(var(--spacing-unit) * 0.5);
  padding-left: 0.5rem;
}

ul li::before {
  content: "";
  position: absolute;
  left: -1.25rem;
  top: 0.7em;
  width: 6px;
  height: 6px;
  border-radius: 999px;
  background: linear-gradient(180deg, var(--color-accent-start), var(--color-accent-end));
  box-shadow: 0 0 0 2px color-mix(in srgb, var(--color-accent-end) 15%, transparent);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  margin-top: calc(var(--spacing-unit) * 3);
  padding: var(--spacing-unit) 1rem;
}

.site-footer p {
  max-width: var(--max-width);
  margin-inline: auto;
  font-size: var(--text-sm);
  color: var(--color-text);
  text-align: center;
  margin-bottom: 0;
}

/* Accessibility */
a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: 2px;
}

::selection {
  background-color: rgba(37, 99, 235, 0.2);
  color: var(--color-heading);
}