:root {
    --bg: #0f131a;
    --card: rgba(255, 255, 255, 0.08);
    --text: #e8f0fa;
    --accent: #10b981;
    --shadow: rgba(16, 185, 129, 0.35);
    --ease: cubic-bezier(0.25, 1, 0.5, 1);
}

body.light {
    --bg: #f8fafc;
    --card: rgba(255, 255, 255, 0.75);
    --text: #0f172a;
    --accent: #3b82f6;
    --shadow: rgba(59, 130, 246, 0.35);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Inter", -apple-system, BlinkMacSystemFont, sans-serif;
    transition: background 0.4s var(--ease), color 0.4s var(--ease);
}

body {
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
    overflow-x: hidden;
}

/* Hero Section */
.hero {
    text-align: center;
    padding: 6rem 1rem 4rem;
    background: linear-gradient(145deg, var(--accent) 8%, transparent 92%);
    backdrop-filter: blur(18px);
}
.hero h1 {
    font-size: 2.8rem;
    font-weight: 900;
    margin-bottom: 1rem;
}
.hero p {
    font-size: 1.1rem;
    opacity: 0.9;
}
.btn-toggle {
    margin-top: 1rem;
    padding: 8px 14px;
    border: none;
    border-radius: 10px;
    background: var(--card);
    color: var(--text);
    cursor: pointer;
    box-shadow: 0 8px 25px var(--shadow);
}
.btn-toggle:hover {
    background: var(--accent);
    color: #fff;
    transform: translateY(-3px);
}

/* Content */
.content {
    max-width: 950px;
    margin: 3rem auto;
    padding: 0 1rem;
}
.card {
    background: var(--card);
    backdrop-filter: blur(14px);
    border-radius: 18px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 12px 36px var(--shadow);
    border: 1px solid rgba(255, 255, 255, 0.12);
    transform: translateY(0);
}
.card h2 {
    color: var(--accent);
    font-weight: 800;
    margin-bottom: 1rem;
}
.card:hover {
    transform: translateY(-6px);
    box-shadow: 0 18px 50px var(--shadow);
}

/* Code Blocks */
.code-block {
    background: rgba(0, 0, 0, 0.25);
    padding: 1rem;
    border-radius: 10px;
    overflow-x: auto;
    font-family: "JetBrains Mono", monospace;
    color: #d1fae5;
    margin-top: 1rem;
}

/* GitHub Button */
.btn-github {
    display: inline-block;
    background: linear-gradient(90deg, var(--accent), color-mix(in srgb, var(--accent) 40%, var(--text)));
    color: #fff;
    padding: 1rem 2rem;
    border-radius: 12px;
    text-decoration: none;
    font-weight: 600;
    box-shadow: 0 14px 40px var(--shadow);
    transition: all 0.3s var(--ease);
}
.btn-github:hover {
    transform: scale(1.05);
    box-shadow: 0 20px 60px var(--shadow);
}

/* Back Button */
.center-btn {
    display: flex;
    justify-content: center;
    align-items: center;
}
.btn-back {
    background: var(--card);
    border-radius: 14px;
    padding: 12px 22px;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text);
    text-decoration: none;
    box-shadow: 0 8px 24px var(--shadow);
}
.btn-back:hover {
    background: linear-gradient(135deg, var(--accent), color-mix(in srgb, var(--accent) 70%, #fff));
    color: #fff;
    transform: translateY(-5px);
}

/* Footer */
.footer {
    text-align: center;
    padding: 1.8rem;
    opacity: 0.8;
    font-size: 0.9rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

/* Fade-In Animation */
.fade-up {
    opacity: 0;
    transform: translateY(40px);
    transition: opacity 0.8s var(--ease), transform 0.8s var(--ease);
}
.fade-up.visible {
    opacity: 1;
    transform: translateY(0);
}