:root {
    --accent: #ffd700;
    --accent-light: #ffe88b;
    --bg-dark: #1a1a1a;
    --bg-mid: #333;
    --highlight: #00b4d8;
    --text-light: #f0f0f0;
}

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

body {
    font-family: 'Ubuntu', sans-serif;
    background: linear-gradient(135deg, var(--bg-dark), var(--bg-mid));
    color: var(--text-light);
    overflow-x: hidden;
}

/* Floating Navbar */
nav {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(26, 26, 26, 0.85);
    backdrop-filter: blur(8px);
    border-bottom: 1px solid rgba(255, 215, 0, 0.3);
    display: flex;
    justify-content: center;
    padding: 10px 0;
    z-index: 999;
    transition: all 0.3s ease;
}

nav a {
    color: var(--accent);
    text-decoration: none;
    font-weight: 600;
    margin: 0 20px;
    transition: color 0.3s ease, transform 0.2s ease;
    padding-bottom: 4px;
    border-bottom: 2px solid transparent;
}

nav a:hover {
    color: var(--highlight);
    transform: translateY(-2px);
}

/* Active link (based on :target section) */
section:target~nav a[href*="#overview"],
section:target~nav a[href*="#design"],
section:target~nav a[href*="#links"],
section:target~nav a[href*="#footer"] {
    border-bottom: 2px solid var(--highlight);
    color: var(--highlight);
}

/* Header */
header {
    background-color: #6a3800;
    text-align: center;
    padding: 70px 15px 35px;
    color: #fff;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.5);
    margin-top: 45px;
    animation: fadeDown 1s ease;
}

header h1 {
    /* text-decoration: underline wavy var(--accent); */
    font-size: 2rem;
    letter-spacing: 1px;
}

h2 {
    color: var(--accent);
    text-align: center;
    margin: 40px 0 20px;
    animation: fadeIn 1.2s ease;
}

/* Collapsible Sections */
details {
    width: 90%;
    margin: 20px auto;
    background: rgba(255, 255, 255, 0.08);
    border-radius: 12px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.4);
    overflow: hidden;
    transition: all 0.4s ease;
}

summary {
    background: rgba(255, 255, 255, 0.12);
    color: var(--accent-light);
    font-weight: 700;
    padding: 18px 20px;
    font-size: 1.3rem;
    cursor: pointer;
    list-style: none;
    display: flex;
    align-items: center;
    justify-content: space-between;
    transition: background 0.3s ease;
}

summary:hover {
    background: rgba(255, 255, 255, 0.2);
}

details[open] summary {
    background: rgba(255, 215, 0, 0.15);
    color: var(--accent);
}

summary::after {
    content: "▼";
    font-size: 0.9rem;
    color: var(--accent);
}

details[open] summary::after {
    content: "▲";
}

/* Cards inside collapsibles */
.card-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 25px;
    padding: 25px;
    animation: slideUp 1.2s ease;
}

.card {
    background: rgba(255, 255, 255, 0.07);
    border-radius: 12px;
    padding: 20px;
    text-align: center;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.4);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    backdrop-filter: blur(6px);
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: 0 10px 25px rgba(255, 215, 0, 0.3);
}

.card h3 {
    color: var(--accent-light);
    font-size: 1.2rem;
    margin-bottom: 10px;
}

.card ul {
    list-style: none;
    padding: 0;
    margin-top: 8px;
}

.card ul li {
    padding: 5px 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.15);
}

/* Links Section */
.links {
    text-align: center;
    font-size: 1.2rem;
    margin: 50px 0;
    animation: fadeIn 1.5s ease;
}

.links a {
    color: var(--accent);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.3s ease;
}

.links a:hover {
    color: var(--highlight);
}

.links hr {
    width: 60%;
    border: 0;
    height: 1px;
    background: linear-gradient(to right, transparent, var(--accent), transparent);
    margin: 25px auto;
}

/* Footer */
footer {
    background-color: #6a3800;
    text-align: center;
    padding: 25px;
    font-size: 1rem;
    box-shadow: 0 -4px 15px rgba(0, 0, 0, 0.4);
    animation: fadeUp 1s ease;
}

footer a {
    color: var(--accent);
    font-weight: bold;
}

footer p {
    margin-top: 10px;
    font-size: 0.9rem;
    color: #ffd700;
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

@keyframes fadeDown {
    from {
        transform: translateY(-40px);
        opacity: 0;
    }

    to {
        transform: translateY(0);
        opacity: 1;
    }
}

@keyframes fadeUp {
    from {
        transform: translateY(40px);
        opacity: 0;
    }

    to {
        transform: translateY(0);
        opacity: 1;
    }
}

@keyframes slideUp {
    from {
        transform: translateY(60px);
        opacity: 0;
    }

    to {
        transform: translateY(0);
        opacity: 1;
    }
}

/* Responsive */
@media (max-width: 600px) {
    header h1 {
        font-size: 1.5rem;
    }

    summary {
        font-size: 1.1rem;
    }

    .card h3 {
        font-size: 1.1rem;
    }

    .links hr {
        width: 80%;
    }

    nav a {
        margin: 0 10px;
        font-size: 0.9rem;
    }
}