/* ========================================
   CSS Reset & Base Styles
   ======================================== */

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

:root {
    /* Resend-inspired Color Palette */
    --color-bg-primary: #000000;
    --color-bg-secondary: #0a0a0a;
    --color-bg-tertiary: #141414;
    --color-bg-card: #0f0f0f;

    --color-text-primary: #ffffff;
    --color-text-secondary: #a1a1a1;
    --color-text-tertiary: #737373;

    --color-accent: #00a3ff;
    --color-accent-hover: #0091e6;

    --color-border: #262626;
    --color-border-light: #1f1f1f;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    --spacing-3xl: 6rem;

    /* Typography */
    --font-sans: 'Geist Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', 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: 2rem;
    --font-size-4xl: 2.5rem;
    --font-size-5xl: 3.5rem;
    --font-size-6xl: 4.5rem;

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;

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

html {
    scroll-behavior: smooth;
}

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

/* ========================================
   Container & Layout
   ======================================== */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* ========================================
   Hero Section
   ======================================== */

.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: radial-gradient(ellipse at top, rgba(0, 163, 255, 0.15) 0%, transparent 50%),
                linear-gradient(180deg, var(--color-bg-primary) 0%, var(--color-bg-secondary) 100%);
    border-bottom: 1px solid var(--color-border);
    overflow: hidden;
    text-align: center;
}

.hero-content {
    max-width: 900px;
    margin: 0 auto;
}

.hero-title {
    font-size: clamp(3rem, 8vw, 5.5rem);
    font-weight: 700;
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
    line-height: 1.1;
    background: linear-gradient(135deg, var(--color-text-primary) 0%, var(--color-text-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: fadeInUp 0.8s ease-out;
}

.hero-subtitle {
    font-size: var(--font-size-xl);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-lg);
    animation: fadeInUp 0.8s ease-out 0.2s backwards;
}

.subtitle-link {
    color: var(--color-text-primary);
    text-decoration: none;
    transition: color var(--transition-base);
}

.subtitle-link:hover {
    color: var(--color-accent);
}

.hero-description {
    font-size: var(--font-size-lg);
    color: var(--color-text-tertiary);
    max-width: 700px;
    margin: 0 auto;
    line-height: 1.8;
    animation: fadeInUp 0.8s ease-out 0.4s backwards;
}

/* Scroll Indicator */
.scroll-indicator {
    position: absolute;
    bottom: var(--spacing-xl);
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
    color: var(--color-text-tertiary);
    animation: fadeInUp 1s ease-out 1s backwards, bounce 2s ease-in-out 2s infinite;
}

.scroll-arrow {
    color: #ffffff;
}

/* ========================================
   Tutorials Section
   ======================================== */

.tutorials-section {
    padding: var(--spacing-3xl) 0;
    background: var(--color-bg-secondary);
}

.tutorials-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--spacing-xl);
}

.tutorial-card {
    position: relative;
    display: flex;
    flex-direction: column;
    padding: var(--spacing-xl);
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    text-decoration: none;
    color: inherit;
    transition: all var(--transition-base);
    overflow: hidden;
}

.tutorial-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--color-accent) 0%, transparent 100%);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.tutorial-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-4px);
    box-shadow: 0 8px 32px rgba(0, 163, 255, 0.2);
}

.tutorial-card:hover::before {
    opacity: 1;
}

.card-icon {
    margin-bottom: var(--spacing-lg);
    color: var(--color-accent);
}

.card-icon svg,
.card-icon img {
    width: 64px;
    height: 64px;
    filter: brightness(0) saturate(100%) invert(100%);
    transition: filter var(--transition-base);
}

.tutorial-card:hover .card-icon img,
.tutorial-card:hover .card-icon svg {
    filter: brightness(0) saturate(100%) invert(56%) sepia(96%) saturate(3213%) hue-rotate(181deg) brightness(102%) contrast(104%);
}

.card-content {
    flex: 1;
}

.card-title {
    font-size: var(--font-size-2xl);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    letter-spacing: -0.01em;
}

.card-description {
    font-size: var(--font-size-base);
    color: var(--color-text-secondary);
    line-height: 1.7;
    margin-bottom: var(--spacing-md);
}

.card-meta {
    display: flex;
    gap: var(--spacing-xs);
    margin-bottom: var(--spacing-lg);
}

.meta-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    font-size: var(--font-size-xs);
    font-weight: 500;
    color: var(--color-text-tertiary);
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
}

.card-arrow {
    align-self: flex-end;
    color: var(--color-accent);
    transition: transform var(--transition-base);
}

.tutorial-card:hover .card-arrow {
    transform: translateX(4px);
}

/* ========================================
   About Section
   ======================================== */

.about-section {
    padding: var(--spacing-3xl) 0;
    background: var(--color-bg-primary);
    border-top: 1px solid var(--color-border-light);
}

.about-content {
    text-align: center;
}

.section-title {
    font-size: var(--font-size-4xl);
    font-weight: 600;
    margin-bottom: var(--spacing-2xl);
    letter-spacing: -0.01em;
}

.features-row {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-xl);
    margin-top: var(--spacing-2xl);
}

.feature-item {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    text-align: left;
    padding: var(--spacing-lg);
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: all var(--transition-base);
}

.feature-item:hover {
    border-color: var(--color-border);
    transform: translateY(-2px);
}

.feature-icon {
    color: var(--color-accent);
    margin-bottom: var(--spacing-md);
}

.feature-icon svg {
    width: 32px;
    height: 32px;
}

.feature-content {
    flex: 1;
}

.feature-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.feature-text {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    line-height: 1.6;
}

/* ========================================
   Footer
   ======================================== */

.footer {
    padding: var(--spacing-2xl) 0;
    background: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border-light);
}

.footer-content {
    text-align: center;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.footer-copyright {
    font-size: var(--font-size-sm);
    color: var(--color-text-tertiary);
}

.footer-powered {
    font-size: var(--font-size-sm);
    color: var(--color-text-tertiary);
}

.footer-link {
    color: var(--color-text-secondary);
    text-decoration: none;
    transition: color var(--transition-base);
}

.footer-link:hover {
    color: var(--color-text-primary);
}

/* ========================================
   Animations
   ======================================== */

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes bounce {
    0%, 100% {
        transform: translateX(-50%) translateY(0);
    }
    50% {
        transform: translateX(-50%) translateY(-10px);
    }
}

/* ========================================
   Responsive Design
   ======================================== */

@media (max-width: 768px) {
    :root {
        --font-size-4xl: 2rem;
        --font-size-5xl: 2.5rem;
        --font-size-6xl: 3rem;
    }

    .hero {
        min-height: auto;
        padding: var(--spacing-3xl) 0;
    }

    .scroll-indicator {
        display: none;
    }

    .tutorials-grid {
        grid-template-columns: 1fr;
    }

    .features-row {
        grid-template-columns: 1fr 1fr;
        gap: var(--spacing-md);
    }
}

@media (max-width: 480px) {
    .features-row {
        grid-template-columns: 1fr;
    }

    .container {
        padding: 0 var(--spacing-md);
    }
}

/* ========================================
   Accessibility
   ======================================== */

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

*:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

::selection {
    background: var(--color-accent);
    color: var(--color-text-primary);
}