@import url('https://fonts.googleapis.com/css2?family=Outfit:wght@300;400;600;800&display=swap');

:root {
    --primary: #4F46E5;
    --primary-glow: rgba(79, 70, 229, 0.4);
    --secondary: #9333EA;
    --accent: #06B6D4;
    --bg-dark: #0F172A;
    --bg-card: rgba(30, 41, 59, 0.7);
    --text-main: #F8FAFC;
    --text-muted: #94A3B8;
    --border: rgba(255, 255, 255, 0.1);
    --glass-blur: blur(12px);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
}

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
    scroll-behavior: smooth;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
    width: 6px;
}
::-webkit-scrollbar-track {
    background: var(--bg-dark);
}
::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 10px;
}

/* Background Effects */
.bg-blobs {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    overflow: hidden;
}

.blob {
    position: absolute;
    width: 500px;
    height: 500px;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    border-radius: 50%;
    filter: blur(100px);
    opacity: 0.15;
    animation: move-blobs 20s infinite alternate;
}

.blob-1 { top: -100px; left: -100px; animation-duration: 25s; }
.blob-2 { bottom: -100px; right: -100px; width: 600px; height: 600px; opacity: 0.1; }

@keyframes move-blobs {
    from { transform: translate(0, 0) scale(1.0); }
    to { transform: translate(100px, 50px) scale(1.1); }
}

/* Navigation */
nav {
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 100;
    padding: 1.5rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(15, 23, 42, 0.5);
    backdrop-filter: var(--glass-blur);
    border-bottom: 1px border var(--border);
}

.nav-logo {
    font-weight: 800;
    font-size: 1.5rem;
    letter-spacing: -0.05em;
    background: linear-gradient(to right, var(--primary), var(--accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-muted);
    font-weight: 500;
    transition: var(--transition);
}

.nav-links a:hover, .nav-links a.active {
    color: var(--text-main);
}

/* Hero Section */
.hero {
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0 5%;
    position: relative;
    text-align: center;
}

.hero-content h1 {
    font-size: clamp(3rem, 8vw, 6rem);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 1.5rem;
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-muted);
    max-width: 600px;
    margin: 0 auto 2rem;
}

.hero-img {
    position: absolute;
    width: 100%;
    height: 100%;
    object-fit: cover;
    opacity: 0.1;
    z-index: -1;
}

/* Section Common */
section {
    padding: 6rem 5% 4rem;
    max-width: 1200px;
    margin: 0 auto;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 3rem;
    text-align: center;
}

/* Cards & Content Blocks */
.content-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 24px;
    padding: 2.5rem;
    backdrop-filter: var(--glass-blur);
    transition: var(--transition);
}

.card:hover {
    transform: translateY(-8px);
    border-color: rgba(255, 255, 255, 0.2);
    box-shadow: 0 20px 40px rgba(0,0,0,0.3);
}

.formula-box {
    background: rgba(0, 0, 0, 0.2);
    padding: 1rem;
    border-radius: 12px;
    margin: 1rem 0;
    display: block;
    text-align: center;
    font-size: 1.2rem;
    overflow-x: auto;
}

/* Exercise Section */
.exercise-container {
    background: var(--bg-card);
    border-radius: 32px;
    padding: 3rem;
    max-width: 800px;
    margin: 0 auto;
    position: relative;
    border: 1px solid rgba(255,255,255,0.1);
}

.question-area {
    margin-bottom: 2rem;
}

.options-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.option-btn {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border);
    color: var(--text-main);
    padding: 1.5rem;
    border-radius: 16px;
    cursor: pointer;
    font-family: inherit;
    font-size: 1rem;
    transition: var(--transition);
    text-align: left;
}

.option-btn:hover {
    background: rgba(255, 255, 255, 0.1);
}

.option-btn.correct {
    background: rgba(34, 197, 94, 0.2);
    border-color: #22C55E;
}

.option-btn.wrong {
    background: rgba(239, 68, 68, 0.2);
    border-color: #EF4444;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links { display: none; }
    .options-grid { grid-template-columns: 1fr; }
    .section-title { font-size: 2rem; }
}

footer {
    padding: 4rem 5%;
    text-align: center;
    color: var(--text-muted);
    border-top: 1px solid var(--border);
}

.btn-primary {
    background: var(--primary);
    color: white;
    padding: 1rem 2rem;
    border-radius: 12px;
    text-decoration: none;
    font-weight: 600;
    display: inline-block;
    transition: var(--transition);
}

.btn-primary:hover {
    box-shadow: 0 0 20px var(--primary-glow);
}