/* CSS Reset and Variables */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --secondary-color: #64748b;
    --secondary-hover: #475569;
    --success-color: #10b981;
    --background: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius: 12px;
    --radius-sm: 8px;
    --transition: all 0.2s ease;
}

/* Base Styles */
html {
    font-size: 16px;
}

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

/* Container */
.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 1rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

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

header h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* Main Content */
main {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Card Styles */
.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}

.card h2 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

/* Current Timestamp Section */
.current-time {
    text-align: center;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    color: white;
}

.current-time h2 {
    color: rgba(255, 255, 255, 0.9);
}

.current-timestamp-display {
    margin: 1rem 0;
}

.timestamp-value {
    font-size: 2.5rem;
    font-weight: 700;
    font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
    letter-spacing: -0.5px;
}

.timestamp-ms {
    font-size: 0.875rem;
    opacity: 0.8;
    margin-top: 0.25rem;
}

.current-date {
    font-size: 1rem;
    opacity: 0.9;
    margin-bottom: 1rem;
}

.current-time .btn-secondary {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.current-time .btn-secondary:hover {
    background: rgba(255, 255, 255, 0.3);
}

/* Input Styles */
.input-group {
    margin-bottom: 1rem;
}

.input-group label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.input-with-toggle {
    display: flex;
    gap: 1rem;
    align-items: center;
    flex-wrap: wrap;
}

.input-with-toggle input[type="text"] {
    flex: 1;
    min-width: 200px;
}

input[type="text"],
input[type="date"],
input[type="time"],
select {
    width: 100%;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--card-bg);
    color: var(--text-primary);
    transition: var(--transition);
}

input[type="text"]:focus,
input[type="date"]:focus,
input[type="time"]:focus,
select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

/* Toggle Styles */
.toggle-group {
    display: flex;
    align-items: center;
}

.toggle {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.toggle input[type="checkbox"] {
    width: 1.25rem;
    height: 1.25rem;
    accent-color: var(--primary-color);
    cursor: pointer;
}

/* Date Inputs Grid */
.date-inputs {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1rem;
}

.date-inputs .input-group:last-child {
    grid-column: 1 / -1;
    margin-bottom: 0;
}

@media (min-width: 600px) {
    .date-inputs {
        grid-template-columns: 1fr 1fr 1fr;
    }

    .date-inputs .input-group:last-child {
        grid-column: auto;
    }
}

/* Button Styles */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    font-size: 0.9375rem;
    font-weight: 500;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
}

.btn-icon {
    font-size: 1rem;
}

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

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

.btn-secondary {
    background: var(--card-bg);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--background);
}

.btn-copy {
    padding: 0.5rem 0.75rem;
    font-size: 0.75rem;
}

/* Result Styles */
.result {
    margin-top: 1rem;
    padding: 1rem;
    background: var(--background);
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
}

.result-placeholder {
    color: var(--text-secondary);
    font-style: italic;
    text-align: center;
}

.result-content {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.result-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

.result-row:last-child {
    border-bottom: none;
}

.result-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.result-value {
    font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
    font-size: 0.9375rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Format Reference Table */
.format-reference {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.875rem;
}

th, td {
    text-align: left;
    padding: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

th {
    font-weight: 600;
    color: var(--text-secondary);
    background: var(--background);
}

td {
    font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
}

tbody tr:last-child td {
    border-bottom: none;
}

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

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

footer p {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

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

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

/* Toast Notification */
.toast {
    position: fixed;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--text-primary);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    opacity: 0;
    transition: all 0.3s ease;
    z-index: 1000;
    box-shadow: var(--shadow-lg);
}

.toast.show {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
}

/* Mobile Responsive */
@media (max-width: 600px) {
    .container {
        padding: 1rem;
    }

    header h1 {
        font-size: 1.5rem;
    }

    .timestamp-value {
        font-size: 1.75rem;
    }

    .card {
        padding: 1rem;
    }

    .input-with-toggle {
        flex-direction: column;
        align-items: stretch;
    }

    .input-with-toggle input[type="text"] {
        min-width: 100%;
    }

    .result-row {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.25rem;
    }

    .result-value {
        width: 100%;
        justify-content: space-between;
    }

    table {
        font-size: 0.8125rem;
    }

    th, td {
        padding: 0.5rem;
    }
}

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

.card {
    animation: fadeIn 0.3s ease forwards;
}

.card:nth-child(1) { animation-delay: 0.05s; }
.card:nth-child(2) { animation-delay: 0.1s; }
.card:nth-child(3) { animation-delay: 0.15s; }
.card:nth-child(4) { animation-delay: 0.2s; }

/* Selection */
::selection {
    background: var(--primary-color);
    color: white;
}