/* ============================================================
   KITTERTOOLS — Design System
   main.css: variables, reset, layout, typography, theme
   ============================================================ */

/* ── Theme Variables ─────────────────────────────────────── */
:root {
  /* Colors — Light */
  --bg: #f5f5f7;
  --bg-secondary: #ebebed;
  --surface: #ffffff;
  --surface-raised: #ffffff;
  --border: #d1d1d6;
  --border-subtle: #e5e5ea;
  --text-primary: #1c1c1e;
  --text-secondary: #6e6e73;
  --text-tertiary: #98989d;
  --text-inverse: #ffffff;

  /* Accent — Indigo */
  --accent: #6366f1;
  --accent-hover: #4f46e5;
  --accent-subtle: #eef2ff;
  --accent-subtle-border: #c7d2fe;

  /* Semantic */
  --success: #10b981;
  --success-subtle: #d1fae5;
  --warning: #f59e0b;
  --warning-subtle: #fef3c7;
  --danger: #ef4444;
  --danger-subtle: #fee2e2;

  /* Category colors */
  --cat-text: #8b5cf6;
  --cat-text-bg: #ede9fe;
  --cat-image: #06b6d4;
  --cat-image-bg: #cffafe;
  --cat-network: #10b981;
  --cat-network-bg: #d1fae5;
  --cat-css: #f59e0b;
  --cat-css-bg: #fef3c7;
  --cat-math: #db2777;
  --cat-math-bg: #fce7f3;
  --cat-physics: #ea580c;
  --cat-physics-bg: #fff7ed;

  /* Typography */
  --font-sans: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", "Cascadia Code", "Consolas", monospace;

  /* Spacing */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0,0,0,.06), 0 1px 3px rgba(0,0,0,.08);
  --shadow-md: 0 4px 6px rgba(0,0,0,.05), 0 10px 15px rgba(0,0,0,.08);
  --shadow-lg: 0 10px 25px rgba(0,0,0,.08), 0 20px 40px rgba(0,0,0,.06);
  --shadow-palette: 0 25px 50px rgba(0,0,0,.18);

  /* Transitions */
  --transition-fast: 120ms ease;
  --transition-base: 200ms ease;
  --transition-slow: 350ms ease;

  /* Layout */
  --nav-height: 58px;
  --container-max: 1200px;
  --container-pad: var(--space-6);
}

[data-theme="dark"] {
  --bg: #0f1117;
  --bg-secondary: #161b22;
  --surface: #1a1d27;
  --surface-raised: #22263a;
  --border: #30334d;
  --border-subtle: #22263a;
  --text-primary: #e8eaf0;
  --text-secondary: #9095b0;
  --text-tertiary: #6069a0;
  --text-inverse: #0f1117;

  --accent: #818cf8;
  --accent-hover: #6366f1;
  --accent-subtle: #1e2240;
  --accent-subtle-border: #3730a3;

  --success: #34d399;
  --success-subtle: #064e3b;
  --warning: #fbbf24;
  --warning-subtle: #451a03;
  --danger: #f87171;
  --danger-subtle: #450a0a;

  --cat-text: #a78bfa;
  --cat-text-bg: #2e1065;
  --cat-image: #22d3ee;
  --cat-image-bg: #0e4c5a;
  --cat-network: #34d399;
  --cat-network-bg: #064e3b;
  --cat-css: #fbbf24;
  --cat-css-bg: #451a03;
  --cat-math: #f472b6;
  --cat-math-bg: #500724;
  --cat-physics: #fb923c;
  --cat-physics-bg: #431407;

  --shadow-sm: 0 1px 2px rgba(0,0,0,.3), 0 1px 3px rgba(0,0,0,.25);
  --shadow-md: 0 4px 6px rgba(0,0,0,.25), 0 10px 15px rgba(0,0,0,.3);
  --shadow-lg: 0 10px 25px rgba(0,0,0,.35), 0 20px 40px rgba(0,0,0,.3);
  --shadow-palette: 0 25px 50px rgba(0,0,0,.5);
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--bg);
  transition: background-color var(--transition-base), color var(--transition-base);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img, video, canvas, svg { display: block; max-width: 100%; }

button, input, select, textarea {
  font: inherit;
  color: inherit;
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover { text-decoration: underline; }

/* ── Layout ──────────────────────────────────────────────── */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-pad);
}

/* ── Navigation ──────────────────────────────────────────── */
.app-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-height);
  background: var(--surface);
  border-bottom: 1px solid var(--border-subtle);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  transition: background-color var(--transition-base), border-color var(--transition-base);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  text-decoration: none;
}

.nav-logo:hover { text-decoration: none; color: var(--accent); }

.nav-logo-icon {
  width: 28px;
  height: 28px;
  background: var(--accent);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 0.875rem;
  font-weight: 800;
  font-family: var(--font-mono);
  flex-shrink: 0;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.nav-search-hint {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.8125rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: border-color var(--transition-fast), background var(--transition-fast);
  white-space: nowrap;
}

.nav-search-hint:hover {
  border-color: var(--accent);
  background: var(--accent-subtle);
  color: var(--text-primary);
}

.nav-search-hint .kbd {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 5px;
}

/* ── Hero ─────────────────────────────────────────────────── */
.hero {
  padding: var(--space-16) 0 var(--space-10);
  text-align: center;
}

.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-subtle);
  border: 1px solid var(--accent-subtle-border);
  border-radius: var(--radius-full);
  padding: var(--space-1) var(--space-3);
  margin-bottom: var(--space-5);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1.1;
  color: var(--text-primary);
  margin-bottom: var(--space-4);
}

.hero-title span {
  color: var(--accent);
}

.hero-subtitle {
  font-size: clamp(1rem, 2.5vw, 1.125rem);
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto var(--space-8);
  line-height: 1.65;
}

.hero-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-6);
  flex-wrap: wrap;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.hero-stat {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.hero-stat svg {
  width: 16px;
  height: 16px;
  color: var(--accent);
}

/* ── Tool Grid ────────────────────────────────────────────── */
.tools-section {
  padding-bottom: var(--space-16);
}

.tools-section-header {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-5);
  padding-bottom: var(--space-3);
  border-bottom: 1px solid var(--border-subtle);
}

.tools-section-title {
  font-size: 0.8125rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-tertiary);
}

.tools-section-count {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-tertiary);
  background: var(--bg-secondary);
  border-radius: var(--radius-full);
  padding: 1px 8px;
}

.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-4);
}

/* ── Tool Page Layout ─────────────────────────────────────── */
.tool-page {
  max-width: 860px;
  margin: 0 auto;
  padding: var(--space-8) var(--container-pad) var(--space-16);
}

.tool-breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.8125rem;
  color: var(--text-tertiary);
  margin-bottom: var(--space-6);
}

.tool-breadcrumb a {
  color: var(--text-tertiary);
  text-decoration: none;
}

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

.tool-breadcrumb-sep { color: var(--border); }

.tool-header {
  margin-bottom: var(--space-8);
}

.tool-header-top {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  margin-bottom: var(--space-3);
}

.tool-icon-wrapper {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.tool-title {
  font-size: 1.75rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.2;
  color: var(--text-primary);
}

.tool-description {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ── Footer ──────────────────────────────────────────────── */
.app-footer {
  border-top: 1px solid var(--border-subtle);
  padding: var(--space-8) 0;
  margin-top: auto;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  flex-wrap: wrap;
}

.footer-copy {
  font-size: 0.8125rem;
  color: var(--text-tertiary);
}

.footer-links {
  display: flex;
  gap: var(--space-4);
}

.footer-links a {
  font-size: 0.8125rem;
  color: var(--text-tertiary);
  text-decoration: none;
}

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

/* ── Language visibility ─────────────────────────────────── */
.t-it { display: none; }
[data-lang="it"] .t-it { display: revert; }
[data-lang="it"] .t-en { display: none; }

/* Language toggle button */
.btn-lang {
  display: flex;
  align-items: center;
  gap: 3px;
  padding: 4px 10px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--text-secondary);
  cursor: pointer;
  letter-spacing: 0.04em;
  transition: border-color var(--transition-fast), color var(--transition-fast), background var(--transition-fast);
}

.btn-lang:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-subtle);
}

/* ── Utility ─────────────────────────────────────────────── */
[x-cloak] { display: none !important; }

.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;
}

/* ── Responsive ─────────────────────────────────────────── */
@media (max-width: 640px) {
  :root {
    --container-pad: var(--space-4);
  }

  .nav-search-hint span:not(.kbd) {
    display: none;
  }

  .hero {
    padding: var(--space-10) 0 var(--space-8);
  }

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

  .footer-inner {
    flex-direction: column;
    align-items: flex-start;
  }
}