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

:root {
    --bg-deep: #0a0a0f;
    --bg-surface: #12121c;
    --bg-card: #1a1a2e;
    --bg-input: #0f0f1a;
    --border: #2a2a44;
    --border-glow: #00e5ff33;
    --text-primary: #e8e8f0;
    --text-secondary: #8888aa;
    --text-muted: #555570;
    --accent: #00e5ff;
    --accent-dim: #00e5ff22;
    --accent-mid: #00e5ff55;
    --accent2: #ff2d75;
    --accent3: #a855f7;
    --success: #22c55e;
    --warning: #f59e0b;
    --font-display: 'Outfit', sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
}

body {
    background: var(--bg-deep);
    color: var(--text-primary);
    font-family: var(--font-display);
    min-height: 100vh;
    overflow-x: hidden;
    padding-bottom: 80px;
}

/* ── Animated background ── */
body::before {
    content: '';
    position: fixed;
    inset: 0;
    background:
            radial-gradient(ellipse 600px 400px at 20% 20%, #00e5ff08, transparent),
            radial-gradient(ellipse 500px 500px at 80% 70%, #ff2d7508, transparent),
            radial-gradient(ellipse 400px 300px at 50% 50%, #a855f706, transparent);
    pointer-events: none;
    z-index: 0;
}

/* ── Grid lines bg ── */
body::after {
    content: '';
    position: fixed;
    inset: 0;
    background-image:
            linear-gradient(var(--border) 1px, transparent 1px),
            linear-gradient(90deg, var(--border) 1px, transparent 1px);
    background-size: 80px 80px;
    opacity: 0.04;
    pointer-events: none;
    z-index: 0;
}

.app {
    position: relative;
    z-index: 1;
    max-width: 780px;
    margin: 0 auto;
    padding: 40px 24px 60px;
}

/* ── Category Sections ── */
.category {
    margin-bottom: 32px;
    opacity: 0;
    animation: fadeUp 0.5s ease forwards;
}
.category:nth-child(2) { animation-delay: 0.1s; }
.category:nth-child(3) { animation-delay: 0.15s; }
.category:nth-child(4) { animation-delay: 0.2s; }
.category:nth-child(5) { animation-delay: 0.25s; }

.category-label {
    font-family: var(--font-mono);
    font-size: 11px;
    letter-spacing: 3px;
    text-transform: uppercase;
    color: var(--text-muted);
    margin-bottom: 12px;
    padding-left: 4px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.category-label::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--border);
}

.tool-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

/* ── Tool Card ── */
.tool-card {
    display: block;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 20px 24px;
    text-decoration: none;
    color: inherit;
    position: relative;
    overflow: hidden;
    transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.tool-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, var(--accent-dim), transparent 60%);
    opacity: 0;
    transition: opacity 0.3s;
}

.tool-card:hover {
    border-color: var(--accent-mid);
    transform: translateY(-2px);
    box-shadow: 0 8px 32px var(--accent-dim), 0 0 0 1px var(--accent-dim);
}

.tool-card:hover::before { opacity: 1; }

.tool-card:active { transform: translateY(0); }

.tool-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 6px;
    position: relative;
    z-index: 1;
}

.tool-name {
    font-weight: 700;
    font-size: 1.05rem;
    color: var(--text-primary);
    letter-spacing: -0.2px;
}

.tool-card:hover .tool-name { color: var(--accent); } /* Fallback (Encoding) */

.tool-version {
    font-family: var(--font-mono);
    font-size: 11px;
    color: var(--text-muted);
    background: var(--bg-input);
    border: 1px solid var(--border);
    padding: 3px 10px;
    border-radius: 6px;
    letter-spacing: 0.5px;
    white-space: nowrap;
}

.tool-desc {
    font-size: 0.88rem;
    color: var(--text-secondary);
    font-weight: 300;
    line-height: 1.5;
    position: relative;
    z-index: 1;
}

.tool-arrow {
    position: absolute;
    right: 30px;
    top: 65%;
    transform: translateY(-50%) translateX(-6px);
    color: var(--accent); /* Fallback (Encoding) */
    font-size: 1.2rem;
    opacity: 0;
    transition: all 0.3s;
}

.tool-card:hover .tool-arrow {
    opacity: 1;
    transform: translateY(-50%) translateX(0);
}

/* ── Category icon accents ── */
.cat-math .tool-card:hover { border-color: #a855f755; box-shadow: 0 8px 32px #a855f722; }
.cat-math .tool-card:before { background: linear-gradient(135deg, #a855f722, transparent 60%);}
.cat-math .tool-card:hover .tool-name { color: var(--accent3); }
.cat-math .tool-card:hover .tool-arrow { color: var(--accent3); }

.cat-text .tool-card:hover { border-color: #22c55e55; box-shadow: 0 8px 32px #22c55e22; }
.cat-text .tool-card:before { background: linear-gradient(135deg, #22c55e22, transparent 60%);}
.cat-text .tool-card:hover .tool-name { color: var(--success); }
.cat-text .tool-card:hover .tool-arrow { color: var(--success); }

.cat-physics .tool-card:hover { border-color: #eab30855; box-shadow: 0 8px 32px #eab30822; }
.cat-physics .tool-card:before { background: linear-gradient(135deg, #eab30822, transparent 60%);}
.cat-physics .tool-card:hover .tool-name { color: #eab308; }
.cat-physics .tool-card:hover .tool-arrow { color: #eab308; }

.cat-encoding .tool-card:hover { border-color: var(--accent-mid); box-shadow: 0 8px 32px var(--accent-dim); }

/* ── Footer ── */
footer {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 10;
    background: var(--bg-surface);
    border-top: 1px solid var(--border);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 14px 0;
    text-align: center;
}

footer small {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--text-muted);
    letter-spacing: 0.5px;
}

/* ── Animations ── */
@keyframes fadeUp {
    from { opacity: 0; transform: translateY(18px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ── Responsive ── */
@media (max-width: 600px) {
    .app { padding: 24px 16px 80px; }
    .tool-card { padding: 16px 18px; }
    .tool-name { font-size: 0.95rem; }
    .tool-desc { font-size: 0.82rem; }
    .tool-version { font-size: 10px; padding: 2px 8px; }
    .category-label { font-size: 10px; letter-spacing: 2px; }
    .header { display: flex; flex-direction: column; align-items: center; }
    .header .logo { order: 1; width: 100%; }
    .header h1 { order: 3; width: 100%; font-size: 2.4rem; }
    .header .subtitle { order: 4; width: 100%; font-size: 0.85rem; }
}