:root {
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

body {
    background: linear-gradient(-45deg, #ee7752, #e73c7e, #23a6d5, #23d5ab);
    background-size: 400% 400%;
    animation: gradientShift 15s ease infinite;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    min-height: 100vh;
}

@keyframes gradientShift {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

.converter-card {
    max-width: 1000px;
    width: 100%;
    border-radius: 20px;
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
}

.converter-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.2) !important;
}

.bg-gradient-primary {
    background: var(--primary-gradient) !important;
}

.form-select, .form-control {
    border-radius: 15px;
    border: 2px solid rgba(255,255,255,0.2);
    background: rgba(255,255,255,0.95);
    transition: all 0.3s ease;
}

.form-select:focus, .form-control:focus {
    border-color: #667eea;
    box-shadow: 0 0 0 0.2rem rgba(102, 126, 234, 0.25);
    background: white;
}

.input-group-text {
    border-radius: 15px 0 0 15px;
    border: none;
}

#status {
    border-radius: 15px;
    border: none;
    backdrop-filter: blur(6px);
}

/* Cards */
.number-card {
    border-radius: 18px;
    background: rgba(255,255,255,0.9);
    backdrop-filter: blur(12px);
    transition: transform 0.25s ease, box-shadow 0.25s ease;
    /* Border thickness is controlled via Bootstrap border-4 in HTML */
}

.number-card:hover {
    transform: translateY(-6px);
    box-shadow: 0 12px 24px rgba(0,0,0,0.15);
}

.number-card .display-6 {
    word-break: break-all;
}

/* Responsive tweaks */
@media (max-width: 768px) {
    .converter-card {
        margin: 1rem;
    }
}