/* ========================================
   DESIGN SYSTEM & CSS CUSTOM PROPERTIES
   ======================================== */

:root {
  /* Light mode (default) */
  --bg: #f5f8ff;
  --surface: #ffffff;
  --surface-alt: #eaf0fb;
  --border: #ccd9f0;
  --text-primary: #0b1a2e;
  --text-secondary: #4d6480;
  --accent: #1a52e8;
  --accent-hover: #1340c0;
  --accent-soft: #dde8ff;

  /* Typography scale */
  --text-xs: 0.72rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.2rem;
  --text-xl: 1.5rem;
  --text-2xl: 2rem;
  --text-3xl: 2.75rem;
  --text-4xl: 3.75rem;

  /* Spacing scale */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 48px;
  --space-8: 64px;
  --space-9: 96px;
  --space-10: 128px;

  /* Transitions */
  --ease: cubic-bezier(0.4, 0, 0.2, 1);
  --duration-fast: 150ms;
  --duration-base: 250ms;
  --duration-slow: 400ms;
}

html.dark {
  /* Dark mode */
  --bg: #070d18;
  --surface: #0d1825;
  --surface-alt: #111f30;
  --border: #1c2e45;
  --text-primary: #e2ecff;
  --text-secondary: #6a8fb0;
  --accent: #4d84ff;
  --accent-hover: #6b9bff;
  --accent-soft: #0d2040;
}

/* ========================================
   MODERN CSS RESET
   ======================================== */

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  background-color: var(--bg);
  color: var(--text-primary);
  font-family: 'DM Sans', sans-serif;
  font-size: var(--text-base);
  line-height: 1.6;
  transition: background-color var(--duration-base) var(--ease),
              color var(--duration-base) var(--ease);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

button {
  font-family: inherit;
}

a {
  color: inherit;
  text-decoration: none;
}

/* ========================================
   BASE TYPOGRAPHY
   ======================================== */

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: 'DM Serif Display', serif;
  font-weight: 400;
  line-height: 1.1;
}

body {
  font-weight: 400;
}

/* ========================================
   GLOBAL FOCUS VISIBLE
   ======================================== */

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 3px;
}

/* ========================================
   UTILITIES
   ======================================== */

.mono {
  font-family: 'JetBrains Mono', monospace;
  font-size: var(--text-xs);
}

/* ========================================
   SCROLLBAR STYLING
   ======================================== */

::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--surface-alt);
}

::-webkit-scrollbar-thumb {
  background: var(--accent);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--accent-hover);
}

/* ========================================
   NAVIGATION
   ======================================== */

nav#site-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-4) var(--space-7);
  background: transparent;
  border-bottom: 1px solid var(--border);
  transition: background-color var(--duration-base) var(--ease);
}

nav.scrolled {
  background: rgba(205, 217, 240, 0.85);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

html.dark nav.scrolled {
  background: rgba(13, 24, 37, 0.85);
}

.nav-brand {
  font-family: 'DM Serif Display', serif;
  font-size: var(--text-lg);
  color: var(--text-primary);
  text-decoration: none;
  font-weight: 400;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.nav-links a {
  font-family: 'DM Sans', sans-serif;
  font-size: var(--text-sm);
  font-weight: 400;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--duration-base) var(--ease);
}

.nav-links a:hover {
  color: var(--accent);
}

.nav-links a[aria-current="page"] {
  color: var(--accent);
}

#theme-toggle {
  background: linear-gradient(145deg, var(--surface-alt), var(--surface));
  border: 1px solid var(--border);
  border-radius: 999px;
  width: 36px;
  height: 36px;
  font-size: var(--text-sm);
  cursor: pointer;
  color: var(--text-secondary);
  transition: color var(--duration-base) var(--ease),
              background-color var(--duration-base) var(--ease),
              transform var(--duration-fast) var(--ease),
              box-shadow var(--duration-fast) var(--ease);
  padding: var(--space-2);
  display: flex;
  align-items: center;
  justify-content: center;
}

#theme-toggle:hover {
  color: var(--accent);
  background: var(--accent-soft);
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(26, 82, 232, 0.18);
}

#theme-toggle i {
  pointer-events: none;
}

#theme-toggle .theme-icon {
  transition: transform var(--duration-base) var(--ease),
              opacity var(--duration-fast) var(--ease);
}

#theme-toggle:hover .theme-icon {
  transform: rotate(-16deg) scale(1.06);
}

html.dark #theme-toggle {
  background: linear-gradient(145deg, #162940, #0d1825);
}

html.dark #theme-toggle:hover {
  box-shadow: 0 6px 20px rgba(77, 132, 255, 0.24);
}

/* ========================================
   FOOTER
   ======================================== */

.site-footer {
  max-width: 1100px;
  margin: 0 auto;
  padding: var(--space-7) var(--space-7) var(--space-6);
  border-top: 1px solid var(--border);
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

.site-footer p {
  font-size: var(--text-sm);
}

.site-footer a {
  color: var(--accent);
  transition: color var(--duration-base) var(--ease);
}

.site-footer a:hover {
  color: var(--accent-hover);
}

.footer-socials {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.footer-socials a {
  width: 34px;
  height: 34px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface-alt);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-sm);
  color: var(--text-secondary);
  transition: color var(--duration-base) var(--ease),
              border-color var(--duration-base) var(--ease),
              transform var(--duration-fast) var(--ease),
              background-color var(--duration-base) var(--ease);
}

.footer-socials a:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
  transform: translateY(-2px);
}

/* ========================================
   RESPONSIVE
   ======================================== */

@media (max-width: 640px) {
  nav#site-nav {
    padding: var(--space-3) var(--space-4);
  }

  .nav-brand {
    font-size: var(--text-base);
  }

  .nav-links {
    gap: var(--space-4);
  }

  .nav-links a {
    font-size: var(--text-xs);
  }

  .site-footer {
    padding: var(--space-5) var(--space-4);
    flex-direction: column;
    align-items: flex-start;
  }

  .footer-socials {
    gap: var(--space-2);
  }
}