:root {
            /* Algebra Theme Colors */
            --color-x: #f43f5e;       /* Rose (for x terms) */
            --color-x-glow: rgba(244, 63, 94, 0.35);
            --color-const: #10b981;   /* Emerald (for constant terms) */
            --color-const-glow: rgba(16, 185, 129, 0.35);
            --color-accent: #ffb000;  /* Amber */
            --color-accent-glow: rgba(255, 176, 0, 0.35);
        }

        section {
            margin-bottom: 6rem;
            scroll-margin-top: 2rem;
        }

        .section-header {
            display: flex;
            align-items: center;
            gap: 12px;
            margin-bottom: 1.75rem;
        }

        .section-tag {
            font-family: 'JetBrains Mono', monospace;
            font-size: 0.8rem;
            color: var(--color-accent);
            background: rgba(255, 176, 0, 0.1);
            padding: 4px 10px;
            border-radius: 6px;
            border: 1px solid rgba(255, 176, 0, 0.2);
            text-shadow: 0 0 5px var(--color-accent-glow);
        }

        .section-header h2 {
            font-size: 1.75rem;
            font-weight: 700;
        }

        .section-intro {
            color: var(--text-muted);
            margin-bottom: 2rem;
            line-height: 1.6;
            font-size: 1rem;
            max-width: 850px;
        }

        /* Controls styling */
        .controls-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 1rem;
            margin-top: 1.5rem;
        }

        .btn-op {
            background: rgba(255, 255, 255, 0.03);
            color: var(--text-color);
            border: 1px solid var(--card-border);
            padding: 0.6rem;
            border-radius: 10px;
            font-family: 'Outfit', sans-serif;
            font-size: 0.9rem;
            font-weight: 500;
            cursor: pointer;
            transition: all var(--transition-speed) ease;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 6px;
        }

        .btn-op:hover {
            background: rgba(255, 255, 255, 0.08);
            border-color: rgba(255, 255, 255, 0.15);
        }

        .btn-op.x-op {
            color: var(--color-x);
            border-color: rgba(244, 63, 94, 0.2);
        }
        .btn-op.x-op:hover {
            background: rgba(244, 63, 94, 0.08);
            border-color: rgba(244, 63, 94, 0.4);
        }

        .btn-op.const-op {
            color: var(--color-const);
            border-color: rgba(16, 185, 129, 0.2);
        }
        .btn-op.const-op:hover {
            background: rgba(16, 185, 129, 0.08);
            border-color: rgba(16, 185, 129, 0.4);
        }

        .btn-op.accent-op {
            background: var(--color-accent);
            color: var(--bg-color);
            font-weight: 600;
            border: none;
            box-shadow: 0 4px 10px var(--color-accent-glow);
        }
        .btn-op.accent-op:hover {
            transform: translateY(-1px);
            box-shadow: 0 6px 15px rgba(255, 176, 0, 0.3);
            background: var(--color-accent);
        }

        /* Equation layout */
        .eq-display {
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 12px;
            font-size: 1.5rem;
            font-weight: 700;
            padding: 1rem;
            background: rgba(255, 255, 255, 0.015);
            border-radius: 12px;
            border: 1px dashed rgba(255, 255, 255, 0.05);
            margin-bottom: 1.5rem;
        }

        .eq-side {
            display: inline-flex;
            align-items: center;
            gap: 4px;
        }

        .x-term { color: var(--color-x); }
        .const-term { color: var(--color-const); }
        .eq-sign { color: var(--color-accent); }

        /* Step history list */
        .history-list {
            list-style: none;
            display: flex;
            flex-direction: column;
            gap: 0.5rem;
            max-height: 160px;
            overflow-y: auto;
            padding-right: 4px;
        }

        .history-item {
            font-family: 'JetBrains Mono', monospace;
            font-size: 0.8rem;
            padding: 6px 10px;
            border-radius: 6px;
            background: rgba(255, 255, 255, 0.02);
            border: 1px solid rgba(255, 255, 255, 0.04);
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        .history-op {
            color: var(--color-accent);
            font-weight: 600;
        }

        /* Preset buttons */
        .preset-container {
            display: flex;
            gap: 8px;
            margin-bottom: 1.5rem;
            flex-wrap: wrap;
        }

        .btn-preset {
            background: rgba(255, 255, 255, 0.02);
            color: var(--text-muted);
            border: 1px solid var(--card-border);
            padding: 4px 10px;
            border-radius: 6px;
            font-size: 0.8rem;
            cursor: pointer;
            transition: all var(--transition-speed) ease;
        }

        .btn-preset:hover, .btn-preset.active {
            color: var(--text-color);
            background: rgba(255, 255, 255, 0.06);
            border-color: rgba(255, 255, 255, 0.15);
        }

        .custom-loader {
            display: flex;
            gap: 6px;
            margin-top: 1rem;
            align-items: center;
        }

        .custom-input {
            width: 45px;
            background: rgba(0, 0, 0, 0.3);
            border: 1px solid var(--card-border);
            color: var(--text-color);
            font-family: 'JetBrains Mono', monospace;
            font-size: 0.85rem;
            padding: 4px;
            border-radius: 6px;
            text-align: center;
            outline: none;
        }

        .custom-input:focus {
            border-color: var(--color-accent);
        }