/* ==========================================================================
   Design tokens
   ========================================================================== */

:root {
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "Cascadia Code", "Source Code Pro", Menlo, Consolas, monospace;

  --radius-sm: 0.375rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;

  --space-xs: 0.5rem;
  --space-sm: 0.75rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;

  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;

  --header-height: 4rem;
  --container-max: 68rem;
}

[data-theme="dark"] {
  --color-bg: #0f1117;
  --color-bg-alt: #161b26;
  --color-surface: #1c2333;
  --color-border: #2a3347;
  --color-text: #e8ecf4;
  --color-text-muted: #9aa5bd;
  --color-accent: #6ea8fe;
  --color-accent-hover: #8bb9ff;
  --color-accent-subtle: rgba(110, 168, 254, 0.12);
  --color-shadow: rgba(0, 0, 0, 0.35);
  --color-hero-glow: rgba(110, 168, 254, 0.08);
}

[data-theme="light"] {
  --color-bg: #f7f8fb;
  --color-bg-alt: #eef1f7;
  --color-surface: #ffffff;
  --color-border: #d5dbe8;
  --color-text: #1a2233;
  --color-text-muted: #5c6b82;
  --color-accent: #3b6fd9;
  --color-accent-hover: #2d5bb8;
  --color-accent-subtle: rgba(59, 111, 217, 0.1);
  --color-shadow: rgba(26, 34, 51, 0.08);
  --color-hero-glow: rgba(59, 111, 217, 0.06);
}

/* ==========================================================================
   Base
   ========================================================================== */

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.65;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition-base), color var(--transition-base);
}

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

a {
  color: var(--color-accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.15em;
  transition: color var(--transition-fast);
}

a:hover,
a:focus-visible {
  color: var(--color-accent-hover);
}

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

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  z-index: 200;
  padding: var(--space-sm) var(--space-md);
  background: var(--color-accent);
  color: #fff;
  border-radius: var(--radius-sm);
  text-decoration: none;
}

.skip-link:focus {
  top: var(--space-md);
}

.container {
  width: min(100% - 2rem, var(--container-max));
  margin-inline: auto;
}

/* ==========================================================================
   Header
   ========================================================================== */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-height);
  background: color-mix(in srgb, var(--color-bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  height: 100%;
}

.logo {
  font-weight: 700;
  font-size: 1.125rem;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.site-nav {
  margin-inline-start: auto;
}

.nav-list {
  display: flex;
  gap: var(--space-lg);
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-list a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.9375rem;
  font-weight: 500;
}

.nav-list a:hover,
.nav-list a:focus-visible {
  color: var(--color-text);
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: var(--space-xs) var(--space-sm);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-text);
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  transition: background-color var(--transition-fast), border-color var(--transition-fast);
}

.theme-toggle:hover {
  border-color: var(--color-accent);
}

.theme-toggle__icon::before {
  content: "☀";
}

[data-theme="light"] .theme-toggle__icon::before {
  content: "🌙";
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 2.5rem;
  height: 2.5rem;
  padding: 0;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  cursor: pointer;
}

.nav-toggle__bar {
  display: block;
  width: 1.125rem;
  height: 2px;
  margin-inline: auto;
  background: var(--color-text);
  border-radius: 1px;
  transition: transform var(--transition-fast), opacity var(--transition-fast);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(2) {
  opacity: 0;
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.mobile-nav {
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
}

.mobile-nav[hidden] {
  display: none;
}

.mobile-nav__list {
  list-style: none;
  margin: 0;
  padding: var(--space-sm) var(--space-md) var(--space-md);
}

.mobile-nav__list a {
  display: block;
  padding: var(--space-sm) 0;
  color: var(--color-text);
  text-decoration: none;
  font-weight: 500;
}

/* ==========================================================================
   Hero
   ========================================================================== */

.hero {
  position: relative;
  padding-block: var(--space-3xl) var(--space-2xl);
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 80% 60% at 50% 0%, var(--color-hero-glow), transparent);
  pointer-events: none;
}

.hero__inner {
  position: relative;
  animation: fade-up 0.6s ease both;
}

.hero__eyebrow {
  margin: 0 0 var(--space-sm);
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-accent);
}

.hero__title {
  margin: 0;
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.1;
}

.hero__role {
  margin: var(--space-sm) 0 0;
  font-size: clamp(1.125rem, 2.5vw, 1.375rem);
  color: var(--color-text-muted);
  font-weight: 500;
}

.hero__tagline {
  margin: var(--space-lg) 0 0;
  max-width: 36rem;
  font-size: 1.0625rem;
  color: var(--color-text-muted);
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
  margin-top: var(--space-xl);
}

/* ==========================================================================
   Buttons
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  font-size: 0.9375rem;
  font-weight: 600;
  text-decoration: none;
  border: 1px solid transparent;
  transition: background-color var(--transition-fast), border-color var(--transition-fast), transform var(--transition-fast);
}

.btn:hover,
.btn:focus-visible {
  transform: translateY(-1px);
}

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

.btn--primary:hover,
.btn--primary:focus-visible {
  background: var(--color-accent-hover);
  color: #fff;
}

.btn--secondary {
  background: transparent;
  color: var(--color-text);
  border-color: var(--color-border);
}

.btn--secondary:hover,
.btn--secondary:focus-visible {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

/* ==========================================================================
   Sections
   ========================================================================== */

.section {
  padding-block: var(--space-3xl);
}

.section--alt {
  background: var(--color-bg-alt);
}

.section__title {
  margin: 0 0 var(--space-xl);
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.about__content {
  max-width: 42rem;
}

.about__content p {
  margin: 0 0 var(--space-md);
  color: var(--color-text-muted);
}

.about__content p:last-child {
  margin-bottom: 0;
}

/* ==========================================================================
   Skills
   ========================================================================== */

.skills-grid {
  display: grid;
  gap: var(--space-xl);
}

.skills-group__title {
  margin: 0 0 var(--space-md);
  font-size: 0.875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  list-style: none;
  margin: 0;
  padding: 0;
}

.tag-list--compact {
  gap: var(--space-xs);
}

.tag {
  display: inline-block;
  padding: 0.4rem 0.85rem;
  border-radius: 999px;
  font-size: 0.875rem;
  font-weight: 500;
  font-family: var(--font-mono);
  background: var(--color-accent-subtle);
  color: var(--color-accent);
  border: 1px solid color-mix(in srgb, var(--color-accent) 25%, transparent);
}

.tag--small {
  padding: 0.25rem 0.6rem;
  font-size: 0.75rem;
}

/* ==========================================================================
   Projects
   ========================================================================== */

.projects-grid {
  display: grid;
  gap: var(--space-lg);
}

.project-card {
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  box-shadow: 0 4px 24px var(--color-shadow);
  transition: transform var(--transition-base), border-color var(--transition-base);
  animation: fade-up 0.5s ease both;
}

.project-card:nth-child(2) { animation-delay: 0.05s; }
.project-card:nth-child(3) { animation-delay: 0.1s; }
.project-card:nth-child(4) { animation-delay: 0.15s; }

.project-card:hover {
  transform: translateY(-2px);
  border-color: color-mix(in srgb, var(--color-accent) 40%, var(--color-border));
}

.project-card__title {
  margin: 0 0 var(--space-sm);
  font-size: 1.25rem;
  font-weight: 700;
}

.project-card__title a {
  color: var(--color-text);
  text-decoration: none;
}

.project-card__title a:hover,
.project-card__title a:focus-visible {
  color: var(--color-accent);
}

.project-card__description {
  margin: 0 0 var(--space-md);
  color: var(--color-text-muted);
  font-size: 0.9375rem;
}

.project-card__link {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  margin-top: var(--space-md);
  font-size: 0.875rem;
  font-weight: 600;
  text-decoration: none;
}

.project-card__link::after {
  content: "→";
  transition: transform var(--transition-fast);
}

.project-card__link:hover::after,
.project-card__link:focus-visible::after {
  transform: translateX(3px);
}

/* ==========================================================================
   Contact
   ========================================================================== */

.contact__lead {
  margin: 0 0 var(--space-lg);
  color: var(--color-text-muted);
}

.contact-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--space-md);
}

.contact-link {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  padding: var(--space-lg);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  text-decoration: none;
  transition: border-color var(--transition-fast), transform var(--transition-fast);
}

.contact-link:hover,
.contact-link:focus-visible {
  border-color: var(--color-accent);
  transform: translateY(-1px);
}

.contact-link__label {
  font-size: 0.8125rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
}

.contact-link__value {
  font-size: 1.0625rem;
  font-weight: 600;
  color: var(--color-text);
}

/* ==========================================================================
   Footer
   ========================================================================== */

.site-footer {
  padding-block: var(--space-xl);
  border-top: 1px solid var(--color-border);
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
}

.footer__copy {
  margin: 0;
  color: var(--color-text-muted);
}

.footer__repo {
  font-size: 0.875rem;
  font-weight: 500;
  text-decoration: none;
}

/* ==========================================================================
   Animations
   ========================================================================== */

@keyframes fade-up {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* ==========================================================================
   Responsive
   ========================================================================== */

@media (min-width: 640px) {
  .skills-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .projects-grid {
    grid-template-columns: repeat(2, 1fr);
  }

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

@media (min-width: 960px) {
  .skills-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (max-width: 767px) {
  .site-nav {
    display: none;
  }

  .logo {
    margin-inline-end: auto;
  }

  .nav-toggle {
    display: flex;
  }
}

@media (max-width: 374px) {
  .hero__actions {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }
}