:root {
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-accent: #e9ecef;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --text-muted: #adb5bd;
    --border-color: #dee2e6;
    --active-color: #0d6efd;
    --active-glow: rgba(13, 110, 253, 0.3);
    --bit-inactive: #e9ecef;
    --bit-active: #0d6efd;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.12);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 30px rgba(0,0,0,0.15);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    --bg-primary: #1a1d23;
    --bg-secondary: #22262e;
    --bg-accent: #2d3139;
    --text-primary: #e9ecef;
    --text-secondary: #adb5bd;
    --text-muted: #6c757d;
    --border-color: #495057;
    --active-color: #0dcaf0;
    --active-glow: rgba(13, 202, 240, 0.3);
    --bit-inactive: #343a40;
    --bit-active: #0dcaf0;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.3);
    --shadow-lg: 0 10px 30px rgba(0,0,0,0.5);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.container {
    width: 100%;
    max-width: 900px;
    padding: 20px;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 40px;
    padding-bottom: 20px;
    border-bottom: 2px solid var(--border-color);
}

h1 {
    font-size: 2rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--active-color), var(--text-primary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.controls {
    display: flex;
    gap: 15px;
    align-items: center;
}

.btn-icon {
    width: 44px;
    height: 44px;
    border-radius: 12px;
    border: 2px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.btn-icon:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--active-color);
}

.btn-icon svg {
    width: 20px;
    height: 20px;
}

[data-theme="light"] .icon-moon {
    display: none;
}

[data-theme="dark"] .icon-sun {
    display: none;
}

.select {
    padding: 10px 15px;
    border-radius: 10px;
    border: 2px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    transition: var(--transition);
}

.select:hover, .select:focus {
    border-color: var(--active-color);
    outline: none;
}

.clock-display {
    background: var(--bg-secondary);
    border-radius: 20px;
    padding: 40px;
    margin-bottom: 30px;
    box-shadow: var(--shadow-lg);
}

.digital-time {
    font-size: 3rem;
    font-weight: 300;
    text-align: center;
    margin-bottom: 30px;
    font-variant-numeric: tabular-nums;
    letter-spacing: 0.05em;
}

.binary-display {
    display: flex;
    justify-content: center;
    gap: 40px;
}

.binary-column {
    text-align: center;
}

.column-label {
    font-size: 14px;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-secondary);
    margin-bottom: 15px;
    font-weight: 600;
}

.binary-digits {
    display: flex;
    gap: 15px;
}

.binary-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.binary-bit {
    width: 40px;
    height: 40px;
    border-radius: 10px;
    background: var(--bit-inactive);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 18px;
    transition: var(--transition);
    position: relative;
    color: var(--text-muted);
}

.binary-bit.active {
    background: var(--bit-active);
    color: white;
    box-shadow: 0 0 20px var(--active-glow);
    transform: scale(1.05);
}

.binary-bit::before {
    content: attr(data-value);
    position: absolute;
    top: -20px;
    font-size: 10px;
    color: var(--text-muted);
}

.true-binary-display {
    padding: 20px;
}

.true-binary-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
    padding: 15px;
    background: var(--bg-accent);
    border-radius: 12px;
}

.true-binary-label {
    width: 80px;
    font-weight: 600;
    color: var(--text-secondary);
}

.true-binary-bits {
    display: flex;
    gap: 8px;
    flex: 1;
    justify-content: center;
}

.true-binary-bit {
    width: 35px;
    height: 35px;
    border-radius: 8px;
    background: var(--bit-inactive);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 16px;
    transition: var(--transition);
    color: var(--text-muted);
    position: relative;
}

.true-binary-bit.active {
    background: var(--bit-active);
    color: white;
    box-shadow: 0 0 15px var(--active-glow);
}

.true-binary-bit::after {
    content: "2^" attr(data-power);
    position: absolute;
    bottom: -18px;
    font-size: 9px;
    color: var(--text-muted);
}

.decimal-value {
    width: 60px;
    text-align: right;
    font-weight: 700;
    font-size: 20px;
    color: var(--active-color);
}

.mode-controls {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 30px;
    margin-bottom: 30px;
}

.mode-toggle {
    display: flex;
    background: var(--bg-accent);
    border-radius: 12px;
    padding: 4px;
}

.mode-toggle input[type="radio"] {
    display: none;
}

.mode-toggle label {
    padding: 10px 20px;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    font-weight: 500;
    color: var(--text-secondary);
}

.mode-toggle input[type="radio"]:checked + label {
    background: var(--active-color);
    color: white;
    box-shadow: var(--shadow-sm);
}

.btn-secondary {
    padding: 12px 24px;
    border-radius: 12px;
    border: 2px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--active-color);
}

.btn-secondary.active {
    background: var(--active-color);
    color: white;
    border-color: var(--active-color);
}

.educational-panel {
    background: var(--bg-secondary);
    border-radius: 20px;
    padding: 30px;
    margin-bottom: 30px;
    box-shadow: var(--shadow-md);
}

.educational-panel h2 {
    margin-bottom: 20px;
    color: var(--text-primary);
}

.educational-panel h3 {
    margin: 20px 0 15px;
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.educational-content {
    display: grid;
    gap: 20px;
}

.explanation p {
    line-height: 1.8;
    color: var(--text-secondary);
}

.conversion-example {
    background: var(--bg-accent);
    padding: 20px;
    border-radius: 12px;
}

.conversion-row {
    padding: 10px;
    margin-bottom: 10px;
    background: var(--bg-primary);
    border-radius: 8px;
    font-family: 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.6;
}

.conversion-row strong {
    color: var(--active-color);
    display: inline-block;
    width: 80px;
}

footer {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 14px;
}

@media (max-width: 768px) {
    h1 {
        font-size: 1.5rem;
    }
    
    .digital-time {
        font-size: 2rem;
    }
    
    .binary-display {
        flex-direction: column;
        gap: 30px;
    }
    
    .binary-column {
        display: flex;
        align-items: center;
        gap: 20px;
    }
    
    .column-label {
        width: 80px;
        text-align: right;
        margin-bottom: 0;
    }
    
    .mode-controls {
        flex-direction: column;
        gap: 15px;
    }
    
    .true-binary-row {
        flex-direction: column;
        gap: 10px;
        text-align: center;
    }
    
    .true-binary-label {
        width: auto;
    }
    
    .decimal-value {
        width: auto;
    }
}