/* Date Calculator - QuizzMan Tools */
/* Modern CSS with GPU Optimization */

:root {
    --primary: #3b82f6;
    --primary-hover: #2563eb;
    --primary-light: rgba(59, 130, 246, 0.1);
    --primary-glow: rgba(59, 130, 246, 0.25);
    --secondary: #8b5cf6;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --text: #1e293b;
    --text-secondary: #64748b;
    --bg: #f8fafc;
    --surface: #ffffff;
    --border: #e2e8f0;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.12);
    --radius: 12px;
    --radius-lg: 16px;
    --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.dark-mode {
    --text: #f1f5f9;
    --text-secondary: #94a3b8;
    --bg: #0f172a;
    --surface: #1e293b;
    --border: #334155;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.4);
}

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

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
}

/* Header */
header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    contain: layout style;
}

.dark-mode header {
    background: rgba(30, 41, 59, 0.9);
}

.header-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0.75rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo-container a {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    text-decoration: none;
}

.logo {
    height: 40px;
    width: auto;
    transition: transform var(--transition);
}

.logo:hover {
    transform: scale(1.05);
}

.site-title {
    font-size: 1.25rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-actions {
    display: flex;
    gap: 0.5rem;
}

#theme-btn {
    width: 40px;
    height: 40px;
    border: none;
    border-radius: 10px;
    background: var(--primary-light);
    color: var(--primary);
    cursor: pointer;
    font-size: 1rem;
    transition: all var(--transition);
}

#theme-btn:hover {
    background: var(--primary);
    color: white;
    transform: translateY(-2px);
}

/* Container */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
}

/* Page Title */
.page-title {
    text-align: center;
    margin-bottom: 2rem;
}

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

.page-title h1 i {
    color: var(--primary);
    margin-right: 0.5rem;
}

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

/* Tabs */
.tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    background: var(--surface);
    padding: 0.5rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.tab {
    flex: 1;
    padding: 0.75rem 1rem;
    border: none;
    border-radius: 8px;
    background: transparent;
    color: var(--text-secondary);
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.tab:hover {
    background: var(--primary-light);
    color: var(--primary);
}

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

/* Calculator Card */
.calculator-card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

.calculator-card h2 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.calculator-card h2 i {
    color: var(--primary);
}

/* Date Inputs */
.date-inputs {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 1rem;
    align-items: end;
    margin-bottom: 1.5rem;
}

.date-inputs.single {
    grid-template-columns: 1fr;
    max-width: 300px;
    margin: 0 auto 1.5rem;
}

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

.input-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.input-group label i {
    color: var(--primary);
}

.input-group input[type="date"] {
    padding: 0.75rem 1rem;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    font-family: inherit;
    font-size: 1rem;
    color: var(--text);
    background: var(--bg);
    transition: all var(--transition);
}

.input-group input[type="date"]:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 4px var(--primary-light);
}

.separator {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    color: var(--text-secondary);
    font-size: 1.25rem;
}

/* Options Row */
.options-row {
    margin-bottom: 1.5rem;
}

.checkbox-option {
    display: inline-flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1rem;
    background: var(--bg);
    border: 2px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
    transition: all var(--transition);
}

.checkbox-option:hover {
    border-color: var(--primary);
}

.checkbox-option input[type="checkbox"] {
    display: none;
}

.checkmark {
    width: 22px;
    height: 22px;
    border: 2px solid var(--border);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
}

.checkmark::after {
    content: '✓';
    font-size: 14px;
    color: white;
    opacity: 0;
    transform: scale(0);
    transition: all var(--transition);
}

.checkbox-option input:checked + .checkmark {
    background: var(--primary);
    border-color: var(--primary);
}

.checkbox-option input:checked + .checkmark::after {
    opacity: 1;
    transform: scale(1);
}

/* Calculate Button */
.calculate-btn {
    width: 100%;
    padding: 1rem;
    border: none;
    border-radius: var(--radius);
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: white;
    font-family: inherit;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.calculate-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px var(--primary-glow);
}

/* Result Section */
.result-section {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 2px solid var(--border);
}

.result-section h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.result-section h3 i {
    color: var(--primary);
}

.result-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
    margin-bottom: 1rem;
}

.result-item {
    background: var(--bg);
    border-radius: var(--radius);
    padding: 1rem;
    text-align: center;
}

.result-item.highlight {
    background: linear-gradient(135deg, var(--primary-light), rgba(139, 92, 246, 0.1));
    border: 2px solid var(--primary);
}

.result-value {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--primary);
    margin-bottom: 0.25rem;
}

.result-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.result-detail {
    background: var(--primary-light);
    border-radius: 8px;
    padding: 0.75rem 1rem;
    font-size: 0.9rem;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Result Date Display */
.result-date {
    text-align: center;
    padding: 1.5rem;
    background: linear-gradient(135deg, var(--primary-light), rgba(139, 92, 246, 0.1));
    border-radius: var(--radius);
    border: 2px solid var(--primary);
}

.date-display {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 0.5rem;
}

.weekday-display {
    font-size: 1rem;
    color: var(--primary);
    font-weight: 600;
}

/* Operation Section */
.operation-section {
    margin-bottom: 1.5rem;
}

.operation-toggle {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    background: var(--bg);
    padding: 0.25rem;
    border-radius: 10px;
    max-width: 250px;
    margin-left: auto;
    margin-right: auto;
}

.op-btn {
    flex: 1;
    padding: 0.625rem 1rem;
    border: none;
    border-radius: 8px;
    background: transparent;
    color: var(--text-secondary);
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.op-btn:hover {
    color: var(--primary);
}

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

.duration-inputs {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
}

.duration-input {
    text-align: center;
}

.duration-input input {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    font-family: inherit;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text);
    background: var(--bg);
    text-align: center;
    transition: all var(--transition);
}

.duration-input input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 4px var(--primary-light);
}

.duration-input label {
    display: block;
    margin-top: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Weekday Result */
.weekday-result {
    text-align: center;
    padding: 1.5rem;
}

.weekday-badge {
    display: inline-block;
    padding: 0.75rem 2rem;
    font-size: 1.25rem;
    font-weight: 700;
    border-radius: 50px;
    color: white;
    margin-bottom: 1rem;
}

.weekday-badge.day-0 { background: linear-gradient(135deg, #ef4444, #dc2626); }
.weekday-badge.day-1 { background: linear-gradient(135deg, #f59e0b, #d97706); }
.weekday-badge.day-2 { background: linear-gradient(135deg, #10b981, #059669); }
.weekday-badge.day-3 { background: linear-gradient(135deg, #3b82f6, #2563eb); }
.weekday-badge.day-4 { background: linear-gradient(135deg, #8b5cf6, #7c3aed); }
.weekday-badge.day-5 { background: linear-gradient(135deg, #ec4899, #db2777); }
.weekday-badge.day-6 { background: linear-gradient(135deg, #14b8a6, #0d9488); }

.date-formatted {
    font-size: 1.125rem;
    color: var(--text);
    font-weight: 500;
}

.special-info {
    margin-top: 0.5rem;
    font-size: 1rem;
    color: var(--warning);
    font-weight: 600;
}

/* Features Section */
.features-section {
    margin-top: 2rem;
}

.features-section h2 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.features-section h2 i {
    color: var(--warning);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.feature-card {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 1.25rem;
    text-align: center;
    box-shadow: var(--shadow);
    transition: transform var(--transition);
    contain: layout style;
}

.feature-card:hover {
    transform: translateY(-4px);
}

.feature-card i {
    font-size: 2rem;
    color: var(--primary);
    margin-bottom: 0.75rem;
}

.feature-card h4 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 0.5rem;
}

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

/* Footer */
.footer {
    background: var(--surface);
    border-top: 1px solid var(--border);
    padding: 1.5rem;
    margin-top: 3rem;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
}

.dmca-badge img {
    height: 24px;
    opacity: 0.7;
    transition: opacity var(--transition);
}

.dmca-badge:hover img {
    opacity: 1;
}

.footer-links {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: 0.75rem;
}

.footer-links a {
    color: var(--primary);
    text-decoration: none;
    transition: color var(--transition);
}

.footer-links a:hover {
    color: var(--primary-hover);
}

/* Toast */
#toast-container {
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.toast {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.875rem 1.25rem;
    background: var(--surface);
    border-radius: 10px;
    box-shadow: var(--shadow-lg);
    font-size: 0.875rem;
    font-weight: 500;
    animation: slideIn 0.3s ease;
}

.toast.success i { color: var(--success); }
.toast.error i { color: var(--danger); }
.toast.warning i { color: var(--warning); }
.toast.info i { color: var(--primary); }

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(100%);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

/* Responsive */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    .page-title h1 {
        font-size: 1.5rem;
    }

    .tabs {
        flex-direction: column;
    }

    .calculator-card {
        padding: 1rem;
    }

    .date-inputs {
        grid-template-columns: 1fr;
    }

    .separator {
        display: none;
    }

    .result-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .duration-inputs {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    .result-grid {
        grid-template-columns: 1fr 1fr;
        gap: 0.75rem;
    }

    .result-value {
        font-size: 1.5rem;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}