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

:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #64748b;
    --background-color: #0f172a;
    --surface-color: #1e293b;
    --card-color: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border-color: #475569;
    --success-color: #22c55e;
    --error-color: #ef4444;
    --accent-gradient: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 100%);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 0.5rem;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

main {
    flex: 1;
}

.input-section {
    background-color: var(--surface-color);
    border-radius: 1rem;
    padding: 2rem;
    margin-bottom: 2rem;
    border: 1px solid var(--border-color);
}

.ip-version-toggle {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    background-color: var(--card-color);
    padding: 0.25rem;
    border-radius: 0.5rem;
    width: fit-content;
}

.version-btn {
    padding: 0.75rem 1.5rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: 0.375rem;
    transition: all 0.2s ease;
}

.version-btn.active {
    background: var(--accent-gradient);
    color: white;
}

.version-btn:hover:not(.active) {
    color: var(--text-primary);
}

.input-group {
    margin-bottom: 1.5rem;
}

.input-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.input-group input[type="text"],
.input-group input[type="number"] {
    width: 100%;
    padding: 0.875rem 1rem;
    background-color: var(--card-color);
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    color: var(--text-primary);
    font-size: 1rem;
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.cidr-container {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.cidr-slash {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.cidr-container input[type="number"] {
    width: 80px;
    text-align: center;
}

.cidr-container input[type="range"] {
    flex: 1;
    min-width: 150px;
    height: 8px;
    -webkit-appearance: none;
    appearance: none;
    background: var(--card-color);
    border-radius: 4px;
    cursor: pointer;
}

.cidr-container input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    background: var(--primary-color);
    border-radius: 50%;
    cursor: pointer;
    transition: background 0.2s ease;
}

.cidr-container input[type="range"]::-webkit-slider-thumb:hover {
    background: var(--primary-hover);
}

.cidr-container input[type="range"]::-moz-range-thumb {
    width: 20px;
    height: 20px;
    background: var(--primary-color);
    border: none;
    border-radius: 50%;
    cursor: pointer;
}

.calculate-btn {
    width: 100%;
    padding: 1rem;
    background: var(--accent-gradient);
    color: white;
    border: none;
    border-radius: 0.5rem;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.calculate-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.4);
}

.calculate-btn:active {
    transform: translateY(0);
}

.results-section {
    background-color: var(--surface-color);
    border-radius: 1rem;
    padding: 2rem;
    border: 1px solid var(--border-color);
}

.results-section h2 {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1rem;
}

.result-card {
    background-color: var(--card-color);
    padding: 1.25rem;
    border-radius: 0.75rem;
    border: 1px solid var(--border-color);
}

.result-card.wide {
    grid-column: 1 / -1;
}

.result-card h3 {
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-weight: 500;
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.result-value {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    word-break: break-all;
}

.result-value.mono {
    font-family: 'Courier New', Courier, monospace;
    font-size: 1rem;
}

.subnet-table-section {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
}

.subnet-table-section h3 {
    font-size: 1.25rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.table-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.table-controls label {
    color: var(--text-secondary);
}

.table-controls select {
    padding: 0.5rem 1rem;
    background-color: var(--card-color);
    border: 1px solid var(--border-color);
    border-radius: 0.375rem;
    color: var(--text-primary);
    font-size: 1rem;
    cursor: pointer;
}

.divide-btn {
    padding: 0.5rem 1.25rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 0.375rem;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.divide-btn:hover {
    background-color: var(--primary-hover);
}

.table-wrapper {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.9rem;
}

thead {
    background-color: var(--card-color);
}

th, td {
    padding: 0.875rem 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

th {
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    font-size: 0.75rem;
    letter-spacing: 0.05em;
}

td {
    color: var(--text-primary);
}

tbody tr:hover {
    background-color: var(--card-color);
}

footer {
    text-align: center;
    padding: 2rem 0;
    margin-top: 2rem;
    border-top: 1px solid var(--border-color);
}

footer p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s ease;
}

footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Error styling */
.input-group input.error {
    border-color: var(--error-color);
}

.error-message {
    color: var(--error-color);
    font-size: 0.875rem;
    margin-top: 0.25rem;
}

/* Responsive design */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    header h1 {
        font-size: 1.75rem;
    }

    .subtitle {
        font-size: 0.95rem;
    }

    .input-section,
    .results-section {
        padding: 1.25rem;
    }

    .ip-version-toggle {
        width: 100%;
    }

    .version-btn {
        flex: 1;
        padding: 0.625rem 1rem;
    }

    .cidr-container {
        flex-direction: column;
        align-items: stretch;
    }

    .cidr-container input[type="number"] {
        width: 100%;
    }

    .cidr-slash {
        display: none;
    }

    .results-grid {
        grid-template-columns: 1fr;
    }

    .result-card.wide {
        grid-column: 1;
    }

    .table-controls {
        flex-direction: column;
        align-items: stretch;
    }

    .divide-btn {
        width: 100%;
    }

    th, td {
        padding: 0.625rem 0.5rem;
        font-size: 0.8rem;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.5rem;
    }

    .result-value {
        font-size: 1rem;
    }

    .result-value.mono {
        font-size: 0.75rem;
    }
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.results-section {
    animation: fadeIn 0.3s ease-out;
}

/* Custom scrollbar */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--surface-color);
}

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--secondary-color);
}