:root {
    /* Electric Indigo Theme */
    --clr-bg: #0F1219;
    --clr-surface: rgba(30, 41, 59, 0.4);
    --clr-surface-hover: rgba(30, 41, 59, 0.8);
    --clr-border: rgba(99, 102, 241, 0.2);
    --clr-border-strong: rgba(99, 102, 241, 0.5);
    
    --clr-primary: #6366F1;
    --clr-primary-light: #818CF8;
    --clr-accent: #F59E0B;
    
    --clr-text-main: #F8FAFC;
    --clr-text-muted: #94A3B8;
    
    --clr-error: #EF4444;
    --clr-success: #10B981;
    
    --font-sans: 'Inter', system-ui, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    
    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    background-color: var(--clr-bg);
    color: var(--clr-text-main);
    font-family: var(--font-sans);
    line-height: 1.5;
    min-height: 100vh;
    overflow-x: hidden;
    /* Subtle mesh gradient background */
    background-image: 
        radial-gradient(at 0% 0%, rgba(99, 102, 241, 0.15) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(245, 158, 11, 0.1) 0px, transparent 50%);
    background-attachment: fixed;
}

/* Utilities */
.hidden { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); border: 0; }
.mono { font-family: var(--font-mono); }
.mt-3 { margin-top: 0.75rem; }
.mt-4 { margin-top: 1rem; }
.text-sm { font-size: 0.875rem; }
.text-muted { color: var(--clr-text-muted); }
.accent-text { color: var(--clr-accent); }

/* Glass Morphism */
.glass-panel {
    background: var(--clr-surface);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--clr-border);
    border-radius: var(--radius-md);
}

.app-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* Header */
.header {
    padding: 1.5rem 2rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--clr-primary-light);
}

.brand h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--clr-text-main);
    letter-spacing: -0.02em;
}

.subtitle {
    color: var(--clr-text-muted);
    font-size: 0.95rem;
}

/* Layout */
.main-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
    align-items: start;
}

@media (max-width: 900px) {
    .main-content { grid-template-columns: 1fr; }
}

.section-card {
    padding: 1.5rem;
}

.card-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1.25rem;
    color: var(--clr-primary-light);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Inputs */
.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.input-group label {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--clr-text-muted);
}

.input-wrapper {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    background: rgba(0,0,0,0.2);
    padding: 1rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--clr-border);
}

.input-wrapper input[type="text"] {
    width: 100%;
    background: transparent;
    border: none;
    border-bottom: 2px solid var(--clr-border-strong);
    color: var(--clr-text-main);
    font-size: 1.5rem;
    font-family: var(--font-mono);
    padding: 0.5rem 0;
    outline: none;
    transition: var(--transition);
    text-align: center;
}

.input-wrapper input[type="text"]:focus {
    border-bottom-color: var(--clr-primary-light);
    color: var(--clr-primary-light);
}

/* Custom Range Slider */
.prefix-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

#prefix-slider {
    flex-grow: 1;
    -webkit-appearance: none;
    appearance: none;
    height: 6px;
    background: var(--clr-border);
    border-radius: 3px;
    outline: none;
}

#prefix-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--clr-primary);
    cursor: pointer;
    box-shadow: 0 0 10px rgba(99, 102, 241, 0.5);
    transition: var(--transition);
}

#prefix-slider::-webkit-slider-thumb:hover {
    transform: scale(1.1);
    background: var(--clr-primary-light);
}

#prefix-display {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--clr-accent);
    min-width: 3rem;
    text-align: right;
}

.error-msg {
    color: var(--clr-error);
    font-size: 0.85rem;
    margin-top: 0.25rem;
    display: none;
}
.error-msg.visible { display: block; }

/* Details Grid */
.details-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
}

.detail-item {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid rgba(255,255,255,0.05);
}

.detail-item:last-child {
    border-bottom: none;
    padding-bottom: 0;
}

.detail-label {
    font-size: 0.85rem;
    color: var(--clr-text-muted);
}

.detail-value {
    font-size: 0.95rem;
    text-align: right;
    font-weight: 500;
}

.detail-subtext {
    display: block;
    font-size: 0.7rem;
    color: var(--clr-text-muted);
    text-align: right;
    margin-top: 0.15rem;
}

/* Binary Table */
.binary-table {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.bin-row {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.bin-label {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--clr-text-muted);
}

.bin-bits {
    display: flex;
    gap: 0.5rem;
    font-size: 0.95rem;
    letter-spacing: 2px;
}

.bin-octet {
    display: inline-flex;
}

.bit.net { color: var(--clr-text-main); }
.bit.host { color: var(--clr-primary-light); opacity: 0.7; }
.bit.divider { color: var(--clr-border-strong); margin: 0 0.1rem; }

.highlight-row {
    background: rgba(99, 102, 241, 0.1);
    padding: 0.75rem;
    border-radius: var(--radius-sm);
    margin: 0.25rem -0.75rem;
}

/* Legend */
.binary-legend, .map-legend { display: flex; gap: 1.5rem; align-items: center; }
.legend-item { display: flex; align-items: center; gap: 0.5rem; font-size: 0.85rem; color: var(--clr-text-muted); }
.legend-color { width: 12px; height: 12px; border-radius: 3px; }
.net-color { background: var(--clr-text-main); }
.host-color { background: var(--clr-primary-light); opacity: 0.7; }

/* Visual Map */
.space-map-container {
    background: rgba(0,0,0,0.3);
    border: 1px solid var(--clr-border);
    border-radius: var(--radius-sm);
    padding: 1rem;
    min-height: 120px;
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
    align-content: flex-start;
}

.ip-block {
    width: 24px;
    height: 24px;
    border-radius: 4px;
    background: var(--clr-surface-hover);
    border: 1px solid var(--clr-border);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.6rem;
    color: transparent;
    transition: var(--transition);
    cursor: default;
    position: relative;
}

.ip-block:hover {
    transform: scale(1.15);
    z-index: 10;
    color: var(--clr-text-main);
    box-shadow: 0 4px 12px rgba(0,0,0,0.5);
}

.ip-block.network { background: var(--clr-primary); border-color: var(--clr-primary-light); color: #fff;}
.ip-block.broadcast { background: var(--clr-accent); border-color: #FCD34D; color: #000; }
.ip-block.usable { background: rgba(99, 102, 241, 0.15); }
.ip-block.usable:hover { background: rgba(99, 102, 241, 0.5); }

/* Abstract block for large subnets */
.ip-block.abstract {
    width: auto;
    padding: 0 0.5rem;
    font-size: 0.75rem;
    color: var(--clr-text-muted);
    background: transparent;
    border: 1px dashed var(--clr-border-strong);
}

@media (max-width: 500px) {
    .ip-block { width: 18px; height: 18px; }
}