/* ============================================================
   Sudoku-spezial – Shared CSS
   Token System, Reset, Accessibility-Baseline
   ============================================================ */

/* Webfonts */
@font-face {
  font-family: 'Roboto Flex';
  src: url('../fonts/roboto-flex.woff2') format('woff2');
  font-weight: 100 900;
  font-display: swap;
}

:root {
  /* Farb-Tokens (aus SUD-Branding) */
  --blue-main: #2dafe6;
  --blue-dark: #0088cc;
  --blue-mid: #5bbfd6;
  --orange: #e30613;
  --white: #FFFFFF;
  --text-dark: #1A1A1A;
  --text-muted: #555555;
  --bg-light: #F4F8FB;

  /* Typografie */
  --font-primary: 'Roboto Flex', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  --font-size-base: 16px;

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;

  /* Border Radius */
  --radius-sm: 0.5rem;
  --radius-md: 1rem;
  --radius-lg: 1.5rem;

  /* Transitions */
  --transition-base: all 0.2s ease;
  --transition-hover: all 0.3s ease;
}

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

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

html {
  scroll-behavior: smooth;
  font-size: var(--font-size-base);
}

body {
  font-family: var(--font-sans);
  color: var(--text-dark);
  background-color: var(--white);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Headings */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-primary);
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: var(--spacing-sm);
  color: var(--text-dark);
}

h1 { font-size: 3rem; }
h2 { font-size: 2.25rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

p { margin-bottom: var(--spacing-sm); }

/* Links */
a {
  color: var(--blue-main);
  text-decoration: none;
  transition: var(--transition-base);
}

a:hover { color: var(--blue-mid); }
a:active { color: var(--blue-dark); }

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

/* Skip Link (WCAG 2.4.1) */
.skip-link {
  position: absolute;
  top: 0;
  left: 0;
  background-color: var(--blue-main);
  color: var(--white);
  padding: var(--spacing-sm) var(--spacing-md);
  text-decoration: none;
  font-weight: 700;
  z-index: 9999;
  transform: translateY(-100%);
  transition: transform 0.2s ease;
}

.skip-link:focus {
  transform: translateY(0);
}

/* Focus Visible (WCAG 2.4.7) */
a:focus-visible,
button:focus-visible,
[role="button"]:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible,
summary:focus-visible,
[tabindex]:focus-visible {
  outline: 3px solid var(--orange);
  outline-offset: 2px;
  border-radius: 2px;
}

/* Container */
.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

/* Button Styles */
button,
.btn,
[role="button"] {
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition-hover);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background-color: var(--blue-main);
  color: var(--white);
}

.btn-primary:hover {
  background-color: var(--blue-dark);
  transform: translateY(-2px);
}

.btn-secondary {
  background-color: var(--white);
  color: var(--blue-main);
  border: 2px solid var(--blue-main);
}

.btn-secondary:hover {
  background-color: var(--bg-light);
  transform: translateY(-2px);
}

/* Back-to-Top Button */
.back-to-top {
  position: fixed;
  bottom: -60px;
  right: var(--spacing-lg);
  width: 50px;
  height: 50px;
  background-color: var(--blue-main);
  color: var(--white);
  border: none;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: bottom 0.3s ease, background-color 0.3s ease;
  z-index: 40;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.back-to-top.visible { bottom: var(--spacing-lg); }
.back-to-top:hover { background-color: var(--blue-dark); }

/* Animations */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.reveal { animation: fadeInUp 0.8s ease-out forwards; }

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* Responsive */
@media (max-width: 768px) {
  h1 { font-size: 2rem; }
  h2 { font-size: 1.5rem; }
  h3 { font-size: 1.25rem; }
  .container { padding: 0 var(--spacing-md); }
}

@media (max-width: 480px) {
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.25rem; }
  .container { padding: 0 var(--spacing-sm); }
}