/* =========================================
   1. CSS Custom Properties (Design Tokens)
   ========================================= */

:root {
  /* Colori — light theme (WCAG AA compliant) */
  --color-bg: #ffffff;
  --color-surface: #f5f5f5;
  --color-border: #dddddd;
  --color-text: #1a1a1a;          /* contrasto vs bianco: 16.1:1 ✓ */
  --color-text-muted: #555555;    /* contrasto vs bianco: 7.5:1 ✓ */
  --color-accent: #0057b8;        /* contrasto vs bianco: 5.4:1 ✓ AA */
  --color-accent-hover: #003f8a;

  /* Tipografia */
  --font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-size-base: 1rem;         /* 16px */
  --font-size-sm: 0.875rem;       /* 14px */
  --font-size-lg: 1.125rem;       /* 18px */
  --font-size-xl: 1.5rem;         /* 24px */
  --font-size-2xl: 2rem;          /* 32px */
  --line-height: 1.6;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2.5rem;
  --space-2xl: 4rem;

  /* Layout */
  --max-width: 720px;
  --header-height: 60px;

  /* Transizioni */
  --transition: 200ms ease;
}

[data-theme="dark"] {
  --color-bg: #121212;
  --color-surface: #1e1e1e;
  --color-border: #2e2e2e;
  --color-text: #f0f0f0;          /* contrasto vs #121212: 15.8:1 ✓ */
  --color-text-muted: #aaaaaa;    /* contrasto vs #121212: 8.1:1 ✓ */
  --color-accent: #4d9fff;        /* contrasto vs #121212: 7.2:1 ✓ */
  --color-accent-hover: #80bbff;
}

/* =========================================
   2. Reset
   ========================================= */

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

html {
  scroll-behavior: smooth;
  font-size: 100%;
  scroll-padding-top: var(--header-height);
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition), color var(--transition);
}

ul, ol {
  list-style: none;
}

a {
  color: var(--color-accent);
  text-decoration: underline;
  text-underline-offset: 3px;
  transition: color var(--transition);
}

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

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

/* =========================================
   3. Accessibilità — Skip Link
   ========================================= */

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  background: var(--color-accent);
  color: var(--color-bg);
  padding: var(--space-sm) var(--space-md);
  border-radius: 0 0 4px 4px;
  font-weight: 600;
  z-index: 1000;
  text-decoration: none;
  transition: top var(--transition);
}

.skip-link:focus {
  top: 0;
}

/* =========================================
   4. Accessibilità — Focus Visibile
   ========================================= */

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

/* =========================================
   5. Layout — Contenitore centrato
   ========================================= */

.section-inner,
.header-inner,
.footer-inner {
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

/* =========================================
   6. Header
   ========================================= */

header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
  transition: background-color var(--transition), border-color var(--transition);
}

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

.header-identity {
  display: flex;
  flex-direction: column;
  line-height: 1.2;
  margin-right: auto;
}

.header-name {
  font-weight: 700;
  font-size: var(--font-size-base);
}

.header-title {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

header nav ul {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
}

header nav a {
  font-size: var(--font-size-sm);
  text-decoration: none;
  color: var(--color-text-muted);
  white-space: nowrap;
}

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

/* =========================================
   7. Theme Toggle Button
   ========================================= */

#theme-toggle {
  background: none;
  border: 1px solid var(--color-border);
  border-radius: 6px;
  cursor: pointer;
  padding: var(--space-xs) var(--space-sm);
  font-size: var(--font-size-lg);
  line-height: 1;
  color: var(--color-text);
  flex-shrink: 0;
  transition: border-color var(--transition), background-color var(--transition);
}

#theme-toggle:hover {
  background-color: var(--color-border);
}

/* Mostra solo l'icona corretta */
[data-theme="light"] .icon-moon { display: none; }
[data-theme="dark"] .icon-sun  { display: none; }

/* =========================================
   8. Sezioni — stile comune
   ========================================= */

main > section {
  padding-block: var(--space-2xl);
  border-bottom: 1px solid var(--color-border);
}

main > section:last-child {
  border-bottom: none;
}

section h2 {
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-xl);
  color: var(--color-text);
}

/* =========================================
   9. About / Hero
   ========================================= */

#about h1 {
  font-size: var(--font-size-2xl);
  margin-bottom: var(--space-sm);
}

.tagline {
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  margin-bottom: var(--space-lg);
}

.bio {
  max-width: 60ch;
  color: var(--color-text-muted);
}

/* =========================================
   10. Timeline (Esperienza e Formazione)
   ========================================= */

.timeline {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.timeline-item {
  display: grid;
  grid-template-columns: 160px 1fr;
  gap: var(--space-lg);
}

.timeline-date {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  padding-top: 3px; /* allineamento visivo con il titolo */
}

.timeline-role {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.timeline-company {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-sm);
}

.timeline-desc {
  font-size: var(--font-size-base);
  color: var(--color-text-muted);
}

/* =========================================
   11. Skills
   ========================================= */

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--space-lg);
}

.skill-group dt {
  font-weight: 600;
  margin-bottom: var(--space-xs);
  font-size: var(--font-size-sm);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
}

.skill-group dd {
  color: var(--color-text);
  line-height: 1.8;
}

/* =========================================
   12. Contact
   ========================================= */

.contact-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-lg);
}

.contact-list a {
  font-size: var(--font-size-lg);
}

/* =========================================
   13. Footer
   ========================================= */

footer {
  background-color: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding-block: var(--space-xl);
  transition: background-color var(--transition), border-color var(--transition);
}

footer a {
  display: inline-block;
  padding: var(--space-sm) var(--space-lg);
  background-color: var(--color-accent);
  color: var(--color-bg);
  text-decoration: none;
  border-radius: 6px;
  font-weight: 600;
  transition: background-color var(--transition);
}

footer a:hover {
  background-color: var(--color-accent-hover);
  color: var(--color-bg);
}

/* =========================================
   14. Responsive
   ========================================= */

@media (max-width: 640px) {
  :root {
    --font-size-2xl: 1.5rem;
    --space-2xl: 2.5rem;
  }

  .header-inner {
    flex-wrap: wrap;
    height: auto;
    padding-block: var(--space-sm);
    gap: var(--space-sm);
  }

  header {
    height: auto;
  }

  header nav {
    order: 3;
    width: 100%;
  }

  header nav ul {
    gap: var(--space-sm);
  }

  .timeline-item {
    grid-template-columns: 1fr;
    gap: var(--space-xs);
  }

  .timeline-date {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
  }

  .skills-grid {
    grid-template-columns: 1fr 1fr;
  }

  .contact-list {
    flex-direction: column;
    gap: var(--space-md);
  }

  html {
    scroll-padding-top: 120px; /* header height increases when nav wraps */
  }
}

/* =========================================
   15. Accessibilità — Reduced Motion
   ========================================= */

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition: none !important;
    animation: none !important;
  }

  html {
    scroll-behavior: auto;
  }
}