/* ===================================
   CSS Variables & Root Styles
   =================================== */

:root {
  /* Color System */
  --color-bg-primary: #0f172a;      /* slate-900 */
  --color-bg-secondary: #020617;    /* slate-950 */
  --color-surface: rgba(30, 41, 59, 0.4);  /* slate-800/40 */

  --color-primary: #a855f7;         /* purple-500 */
  --color-primary-hover: #9333ea;   /* purple-600 */
  --color-accent: #6366f1;          /* indigo-500 */

  --color-text-primary: #ffffff;
  --color-text-secondary: #cbd5e1;  /* slate-300 */
  --color-text-muted: #94a3b8;      /* slate-400 */

  --color-border: rgba(148, 163, 184, 0.2);
  --color-border-hover: rgba(148, 163, 184, 0.5);

  /* 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);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
  --shadow-purple: 0 10px 15px -3px rgba(168, 85, 247, 0.25);

  /* Border Radius */
  --radius-sm: 0.5rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;

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

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 200ms ease;
  --transition-slow: 300ms ease;
}

/* ===================================
   Base Styles
   =================================== */

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ===================================
   Difficulty Buttons
   =================================== */

.difficulty-btn {
  background-color: rgba(51, 65, 85, 0.5);
  color: var(--color-text-secondary);
}

.difficulty-btn:hover {
  background-color: rgba(51, 65, 85, 0.7);
}

.difficulty-btn.active {
  background: var(--color-primary);
  color: white;
  box-shadow: var(--shadow-purple);
}

/* ===================================
   Word Cards
   =================================== */

.word-card {
  background: linear-gradient(to bottom right, rgba(51, 65, 85, 0.5), rgba(30, 41, 59, 0.5));
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1rem;
  text-align: center;
  transition: all var(--transition-base);
}

.word-card:hover {
  border-color: rgba(168, 85, 247, 0.5);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.word-card span {
  color: white;
  font-weight: 500;
  display: block;
  word-break: break-word;
}

.word-card:hover span {
  color: #e9d5ff;
}

/* ===================================
   Custom Range Slider
   =================================== */

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  background: #334155;
  height: 0.5rem;
  border-radius: 0.25rem;
  cursor: pointer;
  width: 100%;
}

/* Slider Track */
input[type="range"]::-webkit-slider-track {
  background: #334155;
  height: 0.5rem;
  border-radius: 0.25rem;
}

input[type="range"]::-moz-range-track {
  background: #334155;
  height: 0.5rem;
  border-radius: 0.25rem;
}

/* Slider Thumb */
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 1.25rem;
  height: 1.25rem;
  border-radius: 50%;
  background: var(--color-primary);
  cursor: pointer;
  margin-top: -0.375rem;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

input[type="range"]::-moz-range-thumb {
  width: 1.25rem;
  height: 1.25rem;
  border-radius: 50%;
  background: var(--color-primary);
  cursor: pointer;
  border: none;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

input[type="range"]:hover::-webkit-slider-thumb {
  background: var(--color-primary-hover);
}

input[type="range"]:hover::-moz-range-thumb {
  background: var(--color-primary-hover);
}

/* ===================================
   Select Dropdown
   =================================== */

select {
  cursor: pointer;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='white' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
  background-size: 1rem;
  padding-right: 2.5rem;
  appearance: none;
}

/* ===================================
   Utility Classes
   =================================== */

.hidden {
  display: none !important;
}

.flex {
  display: flex !important;
}

/* ===================================
   SEO Content Sections
   =================================== */

.seo-section {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: 2rem;
  backdrop-filter: blur(10px);
}

.seo-section h2 {
  color: var(--color-text-primary);
  font-size: 1.875rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.seo-section h3 {
  color: var(--color-text-primary);
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.seo-section p {
  color: var(--color-text-secondary);
  line-height: 1.75;
  margin-bottom: 1.5rem;
}

.seo-section ul {
  list-style: none;
  padding: 0;
}

.seo-section ul li {
  display: flex;
  gap: 0.75rem;
  color: var(--color-text-secondary);
  margin-bottom: 0.75rem;
}

.seo-section ul li::before {
  content: "•";
  color: var(--color-primary);
  font-weight: bold;
  font-size: 1.5rem;
  line-height: 1;
}

/* ===================================
   Step Indicators
   =================================== */

.step-number {
  flex-shrink: 0;
  width: 2rem;
  height: 2rem;
  border-radius: 50%;
  background: rgba(168, 85, 247, 0.2);
  border: 1px solid rgba(168, 85, 247, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #c084fc;
  font-weight: 700;
  font-size: 0.875rem;
}

/* ===================================
   Category Border Accent
   =================================== */

.category-item {
  border-left: 2px solid rgba(168, 85, 247, 0.5);
  padding-left: 1.5rem;
}

/* ===================================
   Check Icon
   =================================== */

.check-icon {
  flex-shrink: 0;
  width: 1.5rem;
  height: 1.5rem;
  color: var(--color-primary);
}

/* ===================================
   FAQ Section
   =================================== */

.faq-item {
  margin-bottom: 1.5rem;
}

.faq-item h3 {
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
}

.faq-item p {
  margin-bottom: 0;
}

/* ===================================
   CTA Section
   =================================== */

.cta-section {
  background: linear-gradient(to bottom right, rgba(168, 85, 247, 0.1), rgba(59, 130, 246, 0.1));
  border: 1px solid rgba(168, 85, 247, 0.2);
}

/* ===================================
   Scrollbar Styling
   =================================== */

::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--color-bg-primary);
}

::-webkit-scrollbar-thumb {
  background: rgba(148, 163, 184, 0.3);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: rgba(148, 163, 184, 0.5);
}

/* Firefox Scrollbar */
* {
  scrollbar-width: thin;
  scrollbar-color: rgba(148, 163, 184, 0.3) var(--color-bg-primary);
}