/* ==========================================================================
   Base Styles - Reset, Typography, Global
   ========================================================================== */

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

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

body {
  font-family: var(--font-body);
  font-size: var(--text-body);
  line-height: var(--line-height-body);
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

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

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-primary-light);
}

ul, ol {
  list-style: none;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: var(--line-height-tight);
  color: var(--color-text);
}

h1 { font-size: var(--text-h1); margin-bottom: var(--space-lg); }
h2 { font-size: var(--text-h2); margin-bottom: var(--space-md); }
h3 { font-size: var(--text-h3); margin-bottom: var(--space-md); }

p {
  margin-bottom: var(--space-md);
}

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

strong, b {
  font-weight: 600;
}

/* Utility Classes */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

.container--narrow {
  max-width: 720px;
}

.section {
  padding: var(--section-pad) 0;
}

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

.section--dark {
  background: var(--gradient-hero);
  color: #fff;
}

.section--dark h1,
.section--dark h2,
.section--dark h3 {
  color: #fff;
}

.text-center { text-align: center; }
.text-muted  { color: var(--color-text-muted); }

.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;
}

/* Scroll Animation */
.fade-in-up {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in-up.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Back to Top Button */
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--gradient-accent);
  color: #fff;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: opacity var(--transition-base), visibility var(--transition-base), transform var(--transition-base);
  z-index: 90;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-xl);
}

.back-to-top svg {
  width: 24px;
  height: 24px;
}

/* Selection */
::selection {
  background: var(--color-primary-light);
  color: #fff;
}

/* ---- Accessibility: skip link & focus visibility ---- */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 2000;
  background: var(--color-primary-dark);
  color: #fff;
  padding: 0.75rem 1.25rem;
  border-radius: 0 0 var(--radius-sm) 0;
  font-weight: 600;
  text-decoration: none;
}
.skip-link:focus {
  left: 0;
}
a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible,
[tabindex]:focus-visible {
  outline: 3px solid var(--color-primary-light);
  outline-offset: 2px;
}