/* ==========================================================================
   Main CSS - Variables, Reset, and Base Styles
   ========================================================================== */

/* CSS Custom Properties (Variables) */
:root {
  /* Colors */
  --color-primary: #2563eb;
  --color-primary-hover: #1d4ed8;
  --color-primary-light: #dbeafe;
  --color-secondary: #64748b;
  --color-success: #22c55e;
  --color-warning: #f59e0b;
  --color-error: #ef4444;

  /* Background colors */
  --color-bg: #f8fafc;
  --color-bg-card: #ffffff;
  --color-bg-dark: #1e293b;

  /* Text colors */
  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --color-text-light: #94a3b8;
  --color-text-inverse: #ffffff;

  /* Border colors */
  --color-border: #e2e8f0;
  --color-border-dark: #cbd5e1;

  /* Spacing */
  --spacing-xs: 4px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
  --spacing-2xl: 48px;

  /* Border radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
  --transition-slow: 350ms ease;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-family-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, monospace;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;

  /* Z-index layers */
  --z-dropdown: 100;
  --z-modal: 200;
  --z-tooltip: 300;
}

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

* {
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.5;
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

p,
h1,
h2,
h3,
h4,
h5,
h6 {
  overflow-wrap: break-word;
}

ul,
ol {
  list-style: none;
}

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

a:hover {
  color: var(--color-primary-hover);
  text-decoration: underline;
}

/* Focus styles for accessibility */
:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Base Layout */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

/* Header */
header {
  background: var(--color-bg-card);
  border-bottom: 1px solid var(--color-border);
  padding: var(--spacing-md) 0;
  position: sticky;
  top: 0;
  z-index: var(--z-dropdown);
}

header h1 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--color-text);
  text-align: center;
  margin-bottom: var(--spacing-sm);
}

/* Main content */
main {
  padding: var(--spacing-lg) 0;
}

/* Section styles */
section {
  background: var(--color-bg-card);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
}

section h2 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--spacing-md);
  padding-bottom: var(--spacing-sm);
  border-bottom: 1px solid var(--color-border);
}

section h3 {
  font-size: var(--font-size-base);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--spacing-sm);
}

/* Track selector */
.track-selector {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
}

.track-selector label {
  font-weight: 500;
  color: var(--color-text-muted);
}

.track-selector select {
  padding: var(--spacing-sm) var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg-card);
  color: var(--color-text);
  min-width: 200px;
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.track-selector select:hover {
  border-color: var(--color-border-dark);
}

.track-selector select:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
  outline: none;
}

/* Button base styles */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-md);
  border: none;
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
  min-height: 44px;
  min-width: 44px;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-secondary {
  background: var(--color-bg);
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--color-border);
}

/* Downloads section */
.downloads {
  margin-top: var(--spacing-lg);
}

.downloads ul {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
}

.downloads li {
  display: inline-block;
}

.downloads a {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text);
  font-size: var(--font-size-sm);
  transition: all var(--transition-fast);
}

.downloads a:hover {
  background: var(--color-primary-light);
  border-color: var(--color-primary);
  color: var(--color-primary);
  text-decoration: none;
}

.downloads a svg {
  width: 16px;
  height: 16px;
}

/* Tips section */
.tips {
  background: var(--color-primary-light);
  border-left: 4px solid var(--color-primary);
  padding: var(--spacing-md);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin-top: var(--spacing-lg);
}

.tips h3 {
  color: var(--color-primary-hover);
  margin-bottom: var(--spacing-sm);
}

.tips ul {
  list-style: disc;
  padding-left: var(--spacing-lg);
}

.tips li {
  color: var(--color-text);
  margin-bottom: var(--spacing-xs);
}

/* Footer */
footer {
  text-align: center;
  padding: var(--spacing-lg) 0;
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  border-top: 1px solid var(--color-border);
  margin-top: var(--spacing-2xl);
}

footer a {
  color: var(--color-text-muted);
}

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

/* Utility classes */
.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;
}

/* PDF Viewer */
.pdf-viewer {
  width: 100%;
  height: 70vh;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
}

.pdf-controls {
  display: flex;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  align-items: center;
}

.pdf-controls select {
  flex: 1;
  padding: var(--spacing-sm) var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg-card);
  color: var(--color-text);
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.pdf-controls select:hover {
  border-color: var(--color-border-dark);
}

.pdf-controls select:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
  outline: none;
}