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

:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #dc2626;
    --accent-color: #f59e0b;
    --accent-light: #fbbf24;
    --text-dark: #1f2937;
    --text-light: #6b7280;
    --white: #ffffff;
    --light-bg: #f8fafc;
    --dark-bg: #0f172a;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --border-radius: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: 'Inter', sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Typography */
.section-title {
    font-size: 3rem;
    text-align: center;
    margin-bottom: 1rem;
    color: var(--text-dark);
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-subtitle {
    text-align: center;
    font-size: 1.25rem;
    color: var(--text-light);
    margin-bottom: 4rem;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* Accessibility: Skip to content link */
.skip-to-content {
    position: absolute;
    left: -9999px;
    top: 0;
    background: var(--primary-color);
    color: #fff;
    padding: 0.75rem 1rem;
    z-index: 10000;
    border-radius: 4px;
}
.skip-to-content:focus {
    left: 1rem;
    top: 1rem;
    outline: 2px solid #fff;
}

/* Back to Top button */
.back-to-top {
    position: fixed;
    right: 20px;
    bottom: 24px;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: none;
    background: var(--primary-color);
    color: #fff;
    cursor: pointer;
    box-shadow: 0 10px 20px rgba(0,0,0,0.15);
    opacity: 0;
    visibility: hidden;
    transform: translateY(12px);
    transition: opacity 0.25s ease, transform 0.25s ease, visibility 0.25s;
    z-index: 9999;
}
.back-to-top:hover {
    background: var(--secondary-color);
}
.back-to-top:focus-visible {
    outline: 2px solid #fff;
    outline-offset: 2px;
}
.back-to-top.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

/* Navbar: focus and active states */
.nav-menu a {
    position: relative;
    outline: none;
}

.nav-menu a:focus-visible {
    box-shadow: 0 0 0 3px rgba(37,99,235,0.35);
    border-radius: var(--border-radius);
}

.nav-menu a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: var(--transition);
    transform: translateX(-50%);
}

.nav-menu a:hover::after {
    width: 80%;
}

.nav-menu a.is-active,
.nav-menu a[aria-current="page"] {
    color: var(--primary-color);
    background: rgba(37, 99, 235, 0.1);
    font-weight: 600;
}

.nav-menu a.is-active::after,
.nav-menu a[aria-current="page"]::after {
    width: 80%;
}

/* Animations */
@keyframes float {
    0%, 100% { transform: translateY(0px) rotate(0deg); }
    50% { transform: translateY(-20px) rotate(180deg); }
}

@keyframes slideInLeft {
    from { opacity: 0; transform: translateX(-50px); }
    to { opacity: 1; transform: translateX(0); }
}

@keyframes slideInRight {
    from { opacity: 0; transform: translateX(50px); }
    to { opacity: 1; transform: translateX(0); }
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .section-title {
        font-size: 2.5rem;
    }
    
    .container {
        padding: 0 15px;
    }
}

@media (max-width: 480px) {
    .section-title {
        font-size: 2rem;
    }
}