:root {
    /* Colors - Premium Dark Palette */
    --bg-dark: #0f1115;
    --bg-card: #181b21;
    --bg-input: #232730;
    --primary: #3b82f6;
    /* Blue */
    --primary-hover: #2563eb;
    --accent: #10b981;
    /* Emerald for results */
    --text-main: #e2e8f0;
    --text-muted: #94a3b8;
    --border: #2d3748;
    --glass: rgba(255, 255, 255, 0.05);

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;

    /* Radius */
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 20px;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-main);
    height: 100vh;
    overflow: hidden;
}

a,
button {
    touch-action: manipulation;
    cursor: pointer;
}

.app-container {
    display: flex;
    height: 100%;
}

/* Sidebar */
.sidebar {
    width: 260px;
    background-color: var(--bg-card);
    border-right: 1px solid var(--border);
    padding: var(--spacing-md);
    display: flex;
    flex-direction: column;
    overflow-y: auto;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-weight: 700;
    font-size: 1.2rem;
    color: var(--text-main);
    margin-bottom: var(--spacing-lg);
}

.logo svg {
    color: var(--primary);
}

.nav-links {
    list-style: none;
}

.nav-links li {
    margin-bottom: var(--spacing-xs);
}

.nav-links a {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm);
    border-radius: var(--radius-sm);
    color: var(--text-muted);
    text-decoration: none;
    transition: all 0.2s ease;
}

.nav-links li.active a {
    background-color: rgba(59, 130, 246, 0.1);
    color: var(--primary);
}

.nav-links a:hover:not(.disabled) {
    background-color: var(--glass);
    color: var(--text-main);
}

.nav-links a.disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Main Content */
.main-content {
    flex: 1;
    padding: var(--spacing-lg);
    padding-bottom: 8rem;
    padding-right: 3rem;
    overflow-y: auto;
}

.top-bar {
    margin-bottom: var(--spacing-lg);
}

.top-bar h1 {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.subtitle {
    color: var(--text-muted);
}

/* Tool Workspace */
.tool-workspace {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
    max-width: 1200px;
}

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

/* Cards */
.card {
    background-color: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

/* Calculator Inputs */
.input-group {
    margin-bottom: var(--spacing-md);
}

.input-group label {
    display: block;
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: var(--spacing-xs);
}

.input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

input[type="number"],
input[type="text"] {
    width: 100%;
    background-color: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 12px;
    padding-right: 40px;
    color: var(--text-main);
    font-family: 'JetBrains Mono', monospace;
    font-size: 1rem;
    transition: border-color 0.2s;
}

input[type="number"]:focus,
input[type="text"]:focus {
    outline: none;
    border-color: var(--primary);
}

.unit {
    position: absolute;
    right: 12px;
    color: var(--text-muted);
    font-size: 0.9rem;
    pointer-events: none;
}

.quick-select {
    display: flex;
    gap: var(--spacing-xs);
    margin-top: var(--spacing-xs);
}

.quick-select button {
    background-color: var(--glass);
    border: 1px solid var(--border);
    color: var(--text-muted);
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.2s;
}

.quick-select button:hover {
    background-color: var(--bg-input);
    color: var(--text-main);
}

/* Result Display */
.result-display {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-md);
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.1) 0%, rgba(16, 185, 129, 0.1) 100%);
    border-radius: var(--radius-md);
    border: 1px solid rgba(59, 130, 246, 0.2);
    text-align: center;
}

.result-label {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: var(--spacing-xs);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.result-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-main);
}

#att-results .result-value {
    font-size: 1.25rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(0, 0, 0, 0.2);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
}

.small-unit {
    font-size: 1rem;
    color: var(--text-muted);
    font-weight: 400;
}

/* Circuit Visualization */
.visual-card h3 {
    margin-bottom: var(--spacing-md);
    font-size: 1.1rem;
    color: var(--text-main);
}

.circuit-diagram {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 300px;
    background-color: var(--bg-input);
    border-radius: var(--radius-sm);
    overflow: hidden;
}

.circuit-image {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
}

/* Analysis Grid */
.analysis-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border);
}

.analysis-item {
    background-color: var(--bg-input);
    padding: var(--spacing-sm);
    border-radius: var(--radius-sm);
    border: 1px solid transparent;
    transition: border-color 0.2s;
}

.analysis-item:hover {
    border-color: var(--glass);
}

.analysis-label {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 4px;
}

.analysis-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-main);
}

.unit-mini {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-weight: 400;
}

/* Tool Sections */
.tool-section {
    display: none;
    animation: fadeIn 0.3s ease;
}

.tool-section.active {
    display: block;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Resistor Calculator Styles */
.mode-selector {
    display: flex;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
    padding-bottom: var(--spacing-md);
    border-bottom: 1px solid var(--border);
}

.radio-label {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    cursor: pointer;
    color: var(--text-muted);
    transition: color 0.2s;
}

.radio-label:hover {
    color: var(--text-main);
}

.radio-label input[type="radio"] {
    accent-color: var(--primary);
}

.resistor-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.resistor-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    animation: slideIn 0.2s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-10px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.resistor-item .input-wrapper {
    flex: 1;
}

.btn-icon {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 4px;
    border-radius: 4px;
    transition: all 0.2s;
}

.btn-icon:hover {
    background-color: rgba(239, 68, 68, 0.1);
    color: #ef4444;
    /* Red */
}

.btn-secondary {
    background-color: var(--glass);
    border: 1px solid var(--border);
    color: var(--text-main);
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s;
    font-size: 0.9rem;
}

.btn-secondary:hover {
    background-color: var(--bg-input);
    border-color: var(--primary);
}

.placeholder-text {
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* Resistor Color Code Styles */
.resistor-band {
    width: 15px;
    height: 100%;
    background-color: transparent;
    transition: background-color 0.3s;
    border-radius: 2px;
}

.color-select {
    width: 100%;
    padding: 8px;
    border-radius: var(--radius-sm);
    background-color: var(--bg-input);
    border: 1px solid var(--border);
    color: var(--text-main);
    cursor: pointer;
}

.color-select option {
    background-color: var(--bg-input);
    color: var(--text-main);
}

/* Navigation Categories */
.nav-category {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-main);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-xs);
    padding-left: var(--spacing-sm);
    opacity: 1;
}

.nav-category:first-child {
    margin-top: 0;
}

/* Premium About Page Redesign */
.about-hero {
    text-align: center;
    padding: 4rem 0;
    position: relative;
}

.about-hero::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 200px;
    height: 200px;
    background: var(--primary);
    filter: blur(100px);
    opacity: 0.2;
    z-index: -1;
    border-radius: 50%;
}

.about-hero h1 {
    font-size: 3.5rem;
    font-weight: 800;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, #fff 0%, #94a3b8 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -1px;
}

.about-hero .subtitle {
    font-size: 1.2rem;
    color: var(--text-muted);
    font-weight: 300;
    letter-spacing: 1px;
}

.glass-card {
    background: rgba(255, 255, 255, 0.03);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: var(--radius-lg);
    padding: 2rem;
    transition: all 0.3s ease;
}

.glass-card:hover {
    background: rgba(255, 255, 255, 0.05);
    border-color: rgba(255, 255, 255, 0.1);
    transform: translateY(-5px);
    box-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
}

.feature-grid-premium {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin: 4rem 0;
}

.feature-item {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.feature-icon {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.feature-item h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-main);
}

.feature-item p {
    color: var(--text-muted);
    line-height: 1.6;
    font-size: 0.95rem;
}



.action-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-top: 4rem;
}

@media (max-width: 768px) {
    .action-grid {
        grid-template-columns: 1fr;
    }
}

.action-card {
    text-align: center;
    position: relative;
    overflow: hidden;
}

.action-card::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, transparent 0%, rgba(255, 255, 255, 0.03) 50%, transparent 100%);
    transform: translateX(-100%);
    transition: transform 0.6s ease;
}

.action-card:hover::after {
    transform: translateX(100%);
}

.qr-container {
    background: #fff;
    padding: 10px;
    border-radius: var(--radius-md);
    display: inline-block;
    margin-top: 1.5rem;
}

.qr-container img {
    display: block;
}

/* Animations */
@keyframes fadeUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.animate-up {
    animation: fadeUp 0.6s ease forwards;
    opacity: 0;
}

.delay-1 {
    animation-delay: 0.1s;
}

.delay-2 {
    animation-delay: 0.2s;
}

.delay-3 {
    animation-delay: 0.3s;
}

/* Helper Text */
.help-text {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: var(--spacing-xs);
    line-height: 1.4;
}

/* Active State for Toggle Buttons */
.btn-secondary.active {
    background-color: rgba(16, 185, 129, 0.2);
    border-color: var(--accent);
    color: var(--accent);
}

/* Logic Gate Selector Grid */
.gate-selector-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
    gap: 0.5rem;
}

.gate-btn {
    background-color: var(--bg-input);
    border: 1px solid var(--border);
    color: var(--text-muted);
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 500;
    transition: all 0.2s;
}

.gate-btn:hover {
    background-color: var(--glass);
    color: var(--text-main);
}

.gate-btn.active {
    background-color: rgba(59, 130, 246, 0.2);
    border-color: var(--primary);
    color: var(--primary);
}

/* Input Count Selector Active State */
.input-count-btn.active {
    background-color: var(--primary);
    color: white;
    border-color: var(--primary);
}

.unit-select {
    background-color: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 12px;
    color: var(--text-main);
    font-family: 'JetBrains Mono', monospace;
    font-size: 1rem;
    cursor: pointer;
    margin-left: 0.5rem;
}

.form-select {
    width: 100%;
    background-color: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 12px;
    color: var(--text-main);
    font-family: 'JetBrains Mono', monospace;
    font-size: 1rem;
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%2394a3b8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    background-size: 16px;
}

/* All Tools Dashboard */
.tool-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.tool-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    cursor: pointer;
    transition: all 0.2s ease;
    text-decoration: none;
    color: var(--text-main);
}

.tool-card:hover {
    transform: translateY(-2px);
    border-color: var(--primary);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.tool-card .icon {
    font-size: 2rem;
    margin-bottom: var(--spacing-xs);
}

.tool-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
}

.tool-card p {
    font-size: 0.9rem;
    color: var(--text-muted);
    line-height: 1.4;
}

.category-header {
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-sm);
    padding-bottom: var(--spacing-xs);
    border-bottom: 1px solid var(--border);
    color: var(--text-muted);
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}