:root {
        --bg-gradient: linear-gradient(135deg, #0f172a 0%, #1e1b4b 100%);
        --card-bg: rgba(255, 255, 255, 0.03);
        --card-border: rgba(255, 255, 255, 0.08);
        --text-main: #f8fafc;
        --text-muted: #94a3b8;
        --accent-blue: #38bdf8;
        --accent-purple: #c084fc;
        --accent-green: #34d399;
    }

    body {
        font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
        line-height: 1.6;
        background: var(--bg-gradient);
        color: var(--text-main);
        margin: 0;
        padding: 3rem 1rem;
        min-height: 100vh;
    }

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

    header {
        text-align: center;
        margin-bottom: 4rem;
    }

    h1 {
        font-size: 2rem;
        font-weight: 800;
        background: linear-gradient(to right, var(--accent-blue), var(--accent-purple));
        -webkit-background-clip: text;
        -webkit-text-fill-color: transparent;
        margin-bottom: 0.5rem;
        letter-spacing: -0.05em;
    }

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

    .card {
        background: var(--card-bg);
        border: 1px solid var(--card-border);
        border-radius: 16px;
        padding: 2.5rem;
        margin-bottom: 2.5rem;
        backdrop-filter: blur(8px);
        box-shadow: 0 4px 30px rgba(0, 0, 0, 0.2);
    }

    h2 {
        margin-top: 0;
        display: flex;
        align-items: center;
        gap: 1rem;
        color: var(--accent-blue);
    }

    .card.yagni-card h2 {
        color: var(--accent-green);
    }

    .acronym {
        font-weight: 400;
        color: var(--text-muted);
        font-size: 1.1rem;
    }

    p {
        color: #cbd5e1;
        font-size: 1.05rem;
    }

    ul {
        list-style-type: none;
        padding: 0;
    }

    li {
        margin-bottom: 0.75rem;
        position: relative;
        padding-left: 1.5rem;
        color: #e2e8f0;
    }

    li::before {
        content: "→";
        position: absolute;
        left: 0;
        color: var(--accent-purple);
        font-weight: bold;
    }

    .yagni-card li::before {
        color: var(--accent-green);
    }

    /* SOLID Detail Styles */
    .solid-grid {
        display: grid;
        gap: 1.5rem;
        margin-top: 2rem;
    }

    .solid-item {
        background: rgba(255, 255, 255, 0.02);
        border-left: 4px solid var(--accent-purple);
        padding: 1.25rem 1.5rem;
        border-radius: 0 12px 12px 0;
    }

    .solid-title {
        font-weight: 700;
        font-size: 1.1rem;
        color: var(--text-main);
        margin-bottom: 0.25rem;
    }

    .solid-letter {
        background: var(--solid-pill-bg);
        color: var(--accent-blue);
        padding: 0.1rem 0.5rem;
        border-radius: 4px;
        margin-right: 0.5rem;
        font-family: monospace;
    }

    .solid-desc {
        color: var(--text-muted);
        margin: 0;
        font-size: 0.95rem;
    }

    footer {
        text-align: center;
        margin-top: 2rem;
        color: var(--text-muted);
        font-size: 0.9rem;
        padding-top: 2rem;
    }

    .public-domain-notice {
        margin-top: 1rem;
        font-size: 0.85rem;
        color: var(--text-muted);
        background: rgba(255, 255, 255, 0.01);
        padding: 1rem;
        border-radius: 8px;
        display: inline-block;
        border: 1px dashed var(--card-border);
    }

    .cc0-icon {
        font-weight: bold;
        letter-spacing: 1px;
        color: var(--accent-blue);
    }

    .back-link-div {
        display: flex; flex-direction: column; align-items: center; gap: 2rem; padding: 1rem;
    }

    .back-link-div button {
        display: inline-flex;
        align-items: center;
        gap: 8px;
        background: #F5C400;
        color: #1a1a1a;
        border: none;
        border-radius: 8px;
        padding: 12px 36px 12px 32px;
        font-size: 15px;
        font-weight: 500;
        cursor: pointer;
        transition: background 0.15s, transform 0.15s;
        font-family: var(--font-sans);
    }

    .back-link-div button:hover {
        background-color: #E0B200;

    }