:root {
    --bg-primary: #0a0f1a;
    --bg-secondary: #111827;
    --bg-card: #1a2234;
    --text-primary: #f3f4f6;
    --text-secondary: #9ca3af;
    --accent: #3b82f6;
    --accent-hover: #2563eb;
    --border: #1f2937;
    --border-light: #374151;
    --success: #22c55e;
    --danger: #ef4444;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 20px;
    min-height: 100vh;
}

.back-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.9rem;
    margin-bottom: 24px;
    transition: color 0.2s;
}
.back-link:hover { color: var(--accent); }

.container {
    max-width: 900px;
    margin: auto;
    background: var(--bg-secondary);
    padding: 32px;
    border: 1px solid var(--border);
    border-radius: 12px;
}

h1 { text-align: center; font-size: 1.75rem; margin-bottom: 24px; }

.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.form-control { display: flex; flex-direction: column; gap: 8px; }
.form-control label { color: var(--text-secondary); font-size: 0.9rem; }

input[type="text"], input[type="number"] {
    width: 100%;
    padding: 10px 12px;
    border-radius: 6px;
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text-primary);
    font-size: 0.95rem;
}
input[type="text"]:focus, input[type="number"]:focus { outline: none; border-color: var(--accent); }

.actions { display: flex; gap: 12px; justify-content: flex-end; margin: 16px 0 8px; }
.calculate-button { background-color: var(--success); padding: 12px 22px; border: none; border-radius: 6px; cursor: pointer; font-weight: 600; }
.calculate-button:hover { background-color: #16a34a; }
.reset-button { background-color: var(--danger); padding: 12px 18px; border: none; border-radius: 6px; cursor: pointer; font-weight: 600; }
.reset-button:hover { background-color: #dc2626; }

.results { margin-top: 24px; }
.hint { color: var(--text-secondary); margin-bottom: 12px; font-size: 0.9rem; }

table { width: 100%; border-collapse: collapse; margin-top: 8px; }
th, td { padding: 12px; text-align: left; border: 1px solid var(--border); }
th { background-color: var(--bg-card); font-weight: 600; font-size: 0.85rem; }
td { background-color: var(--bg-secondary); }

#copy-buttons { display: flex; gap: 12px; justify-content: center; margin: 20px 0 0; }
.copy-button { background-color: var(--accent); border: none; color: white; padding: 10px 16px; border-radius: 6px; cursor: pointer; font-weight: 500; }
.copy-button:hover { background-color: var(--accent-hover); }

/* View toggle */
.view-toggle { display: flex; gap: 8px; margin: 20px 0; }
.toggle-btn { background: var(--bg-card); color: var(--text-primary); border: 1px solid var(--border); padding: 8px 14px; border-radius: 6px; cursor: pointer; }
.toggle-btn.active { border-color: var(--accent); color: white; background: var(--accent); }
.view-section { display: none; }
.view-section.active { display: block; }

/* Subnets */
.subnets-controls { display: flex; align-items: center; gap: 12px; margin-bottom: 12px; }
.subnets-controls input[type="number"] { width: 90px; }

/* Addresses */
.addresses-controls { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; flex-wrap: wrap; }
#addresses-table th, #subnets-table th { background: var(--bg-card); }

/* Bits */
.bits-output { background: var(--bg-card); border: 1px solid var(--border); border-radius: 8px; padding: 16px; font-family: 'Fira Code', monospace; }
.bits-row { display: flex; gap: 10px; align-items: center; margin: 6px 0; flex-wrap: wrap; }
.bits-label { width: 120px; color: var(--text-secondary); }
.bits-binary { display: grid; grid-template-columns: repeat(32, 1fr); gap: 2px; width: 100%; }
.bit { text-align: center; padding: 2px 0; font-size: 0.8rem; border-radius: 2px; }
.bit.net { background: #1e3a8a; color: #bfdbfe; }
.bit.host { background: #374151; color: #e5e7eb; }
.octets { color: var(--text-secondary); font-size: 0.85rem; }

@media (max-width: 640px) {
    .grid-2 { grid-template-columns: 1fr; }
}