/**
 * HK Smart Tools — Base Styles & Reset
 * Premium visual foundation with subtle ambient depth
 */

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

html {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.5;
  color: var(--text-primary);
  background-color: var(--bg-body);
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  background-color: var(--bg-body);
  background-image:
    radial-gradient(ellipse 80% 50% at 50% -15%, rgba(37, 99, 235, 0.08) 0%, transparent 65%),
    radial-gradient(ellipse 60% 40% at 100% 25%, rgba(14, 165, 233, 0.04) 0%, transparent 55%),
    radial-gradient(ellipse 50% 30% at 0% 75%, rgba(99, 102, 241, 0.03) 0%, transparent 50%);
  background-attachment: fixed;
  color: var(--text-primary);
  transition: background-color var(--transition-base), color var(--transition-base);
}

[data-theme="dark"] body {
  background-image:
    radial-gradient(ellipse 80% 50% at 50% -15%, rgba(37, 99, 235, 0.1) 0%, transparent 65%),
    radial-gradient(ellipse 60% 40% at 100% 25%, rgba(14, 165, 233, 0.05) 0%, transparent 55%);
}

/* Accessible Selection */
::selection {
  background-color: var(--primary-100);
  color: var(--primary-900);
}

[data-theme="dark"] ::selection {
  background-color: var(--primary-800);
  color: #ffffff;
}

/* Accessibility Skip Link */
.skip-link {
  position: absolute;
  top: -100px;
  left: var(--space-4);
  background: var(--primary-600);
  color: var(--text-inverse);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-md);
  font-weight: 600;
  z-index: 9999;
  text-decoration: none;
  transition: top var(--transition-fast);
  box-shadow: var(--shadow-lg);
}

.skip-link:focus {
  top: var(--space-4);
  outline: 3px solid var(--accent-400);
}

/* Accessible Focus States */
:focus-visible {
  outline: 2px solid var(--primary-600);
  outline-offset: 2px;
}

/* Typography Defaults */
h1, h2, h3, h4, h5, h6 {
  color: var(--text-primary);
  font-weight: 700;
  line-height: 1.25;
}

h1 {
  font-size: var(--text-3xl);
  letter-spacing: -0.03em;
  margin-bottom: var(--space-3);
  font-weight: 800;
}

@media (min-width: 768px) {
  h1 {
    font-size: var(--text-4xl);
  }
}

h2 {
  font-size: var(--text-2xl);
  letter-spacing: -0.02em;
  margin-top: var(--space-8);
  margin-bottom: var(--space-4);
  font-weight: 700;
}

h3 {
  font-size: var(--text-xl);
  letter-spacing: -0.015em;
  margin-top: var(--space-6);
  margin-bottom: var(--space-3);
  font-weight: 700;
}

p {
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
  line-height: 1.625;
}

p.lead {
  font-size: var(--text-lg);
  color: var(--text-secondary);
  line-height: 1.6;
}

a {
  color: var(--primary-600);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--primary-700);
}

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

ul, ol {
  padding-left: var(--space-6);
  margin-bottom: var(--space-4);
  color: var(--text-secondary);
}

li {
  margin-bottom: var(--space-2);
}

code, kbd, samp, pre {
  font-family: var(--font-mono);
  font-size: 0.9em;
}

code {
  background: var(--bg-surface-subtle);
  color: var(--primary-600);
  padding: 0.15em 0.4em;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-subtle);
}

pre {
  background: var(--bg-surface-subtle);
  padding: var(--space-4);
  border-radius: var(--radius-lg);
  overflow-x: auto;
  border: 1px solid var(--border-subtle);
  margin-bottom: var(--space-4);
}

hr {
  border: 0;
  border-top: 1px solid var(--border-subtle);
  margin: var(--space-8) 0;
}

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

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