:root {
        --bg-color:       #f0f9ff;
        --card-bg:        #ffffff;
        --border-color:   #bae6fd;
        --text-primary:   #0f172a;
        --text-secondary: #475569;
        --accent-color:   #0ea5e9;
        --success-color:  #10b981;
        --danger-color:   #ef4444;
        --radius:         16px;
        --shadow-sm:  0 1px 2px 0 rgba(14,165,233,.05);
        --shadow-md:  0 4px 6px -1px rgba(14,165,233,.1), 0 2px 4px -1px rgba(14,165,233,.06);
        --shadow-lg:  0 10px 15px -3px rgba(14,165,233,.1), 0 4px 6px -2px rgba(14,165,233,.05);
    }
    body {
        background: var(--bg-color);
        font-family: 'Plus Jakarta Sans', sans-serif;
        min-height: 100vh;
        color: var(--text-primary);
    }
    .navbar {
        background: rgba(255,255,255,.85);
        backdrop-filter: blur(12px);
        border-bottom: 1px solid var(--border-color);
        padding: 1rem 0;
        position: sticky;
        top: 0;
        z-index: 100;
        box-shadow: var(--shadow-sm);
    }
    .navbar-brand {
        font-weight: 800;
        font-size: 1.25rem;
        color: var(--accent-color) !important;
        display: flex;
        align-items: center;
        gap: .5rem;
        text-decoration: none;
    }
    .nav-link {
        color: var(--text-secondary) !important;
        font-weight: 600;
        font-size: .95rem;
        margin-left: 1rem;
        transition: color .2s;
    }
    .nav-link:hover, .nav-link.active { color: var(--text-primary) !important; }

    .stack-container {
        max-width: 450px;
        margin: 2rem auto;
        display: flex;
        flex-direction: column;
        gap: 2.5rem;
        padding: 0 0 3rem;
    }
    .stack-card {
        background: var(--card-bg);
        border: 1px solid var(--border-color);
        border-radius: var(--radius);
        padding: 1.5rem;
        box-shadow: var(--shadow-md);
    }

    /* Tabs */
    .nav-tabs { border-bottom: 1px solid var(--border-color); }
    .nav-tabs .nav-link {
        color: var(--text-secondary) !important;
        font-weight: 600;
        border: none;
        border-bottom: 2px solid transparent;
        border-radius: 0;
        padding: .6rem 1.2rem;
        margin-left: 0;
    }
    .nav-tabs .nav-link.active {
        color: var(--accent-color) !important;
        border-bottom: 2px solid var(--accent-color);
        background: transparent;
    }

    /* Form */
    .custom-input {
        width: 100%;
        border: 1px solid var(--border-color);
        background: var(--bg-color);
        border-radius: var(--radius);
        padding: .75rem 1rem;
        font-weight: 600;
        color: var(--text-primary);
        font-family: inherit;
        font-size: 1rem;
        transition: border-color .2s, box-shadow .2s;
    }
    .custom-input:focus {
        outline: none;
        border-color: var(--accent-color);
        background: var(--card-bg);
        box-shadow: 0 0 0 3px rgba(14,165,233,.2);
    }
    .custom-input::placeholder { color: #94a3b8; }

    .btn-main {
        width: 100%;
        background: var(--text-primary);
        color: white;
        border: none;
        padding: .85rem;
        border-radius: var(--radius);
        font-size: 1rem;
        font-weight: 700;
        font-family: inherit;
        transition: all .2s;
        margin-top: .75rem;
        box-shadow: var(--shadow-md);
        cursor: pointer;
    }
    .btn-main:hover {
        background: var(--accent-color);
        transform: translateY(-2px);
        box-shadow: var(--shadow-lg);
    }
    .btn-search {
        background: var(--text-primary);
        color: white;
        border: none;
        padding: .75rem 1.25rem;
        border-radius: var(--radius);
        font-weight: 700;
        font-family: inherit;
        cursor: pointer;
        transition: all .2s;
        white-space: nowrap;
    }
    .btn-search:hover { background: var(--accent-color); }

    /* IDs Table */
    .ids-table { width: 100%; border-collapse: collapse; margin-top: 1rem; }
    .ids-table th {
        background: var(--accent-color);
        color: white;
        padding: .6rem 1rem;
        font-size: .85rem;
        font-weight: 700;
        text-align: left;
    }
    .ids-table td {
        padding: .6rem 1rem;
        font-size: .85rem;
        border-bottom: 1px solid var(--border-color);
        font-weight: 500;
    }
    .ids-table tr:nth-child(even) td { background: #f0f9ff; }

    .copy-btn {
        background: none;
        border: 1px solid var(--border-color);
        border-radius: 6px;
        padding: 2px 8px;
        font-size: .75rem;
        cursor: pointer;
        color: var(--accent-color);
        font-weight: 600;
        transition: all .2s;
    }
    .copy-btn:hover { background: var(--accent-color); color: white; border-color: var(--accent-color); }

    .download-btn {
        display: inline-flex;
        align-items: center;
        gap: .5rem;
        background: #10b981;
        color: white;
        border: none;
        padding: .75rem 1.5rem;
        border-radius: var(--radius);
        font-weight: 700;
        font-family: inherit;
        cursor: pointer;
        transition: all .2s;
        margin-top: 1rem;
    }
    .download-btn:hover { background: #059669; transform: translateY(-2px); }

    .wa-float {
        position: fixed;
        bottom: 2rem; right: 2rem;
        background: #25d366;
        color: white;
        height: 3.5rem; width: 3.5rem;
        border-radius: 50%;
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 1.5rem;
        box-shadow: 0 4px 12px rgba(37,211,102,.4);
        transition: transform .2s;
        z-index: 99;
        text-decoration: none;
    }
    .wa-float:hover { transform: scale(1.05); color: white; }