/* ===============================================
   DATE CALCULATOR - OPTIMIZED FOR PERFORMANCE
   =============================================== */

/* PERFORMANCE: Consolidated color variables */
:root {
    --primary-color: #3B82F6;
    --secondary-color: #10B981;
    --accent-color: #8B5CF6;
    --text-color: #111827;
    --text-secondary: #4B5563;
    --text-tertiary: #6B7280;
    --bg-primary: #FFFFFF;
    --bg-secondary: #F9FAFB;
    --bg-tertiary: #F3F4F6;
    --border-color: #E5E7EB;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --radius-base: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;    
    --radius-2xl: 1.5rem;
    --danger-color: #EF4444;
    --warning-color: #F59E0B;
    --success-color: #10B981;
    --calendar-today: #3B82F6;
    --calendar-selected: #10B981;
    --calendar-weekend: #F59E0B;
    --calendar-holiday: #EF4444;
    --calendar-range: rgba(59, 130, 246, 0.1);
}

/* PERFORMANCE: Optimized dark theme with reduced specificity */
[data-theme="dark"] {
    --text-color: #F9FAFB;
    --text-secondary: #D1D5DB;
    --text-tertiary: #9CA3AF;
    --bg-primary: #111827;
    --bg-secondary: #1F2937;
    --bg-tertiary: #374151;
    --border-color: #374151;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3);
    --calendar-range: rgba(59, 130, 246, 0.2);
}

/* PERFORMANCE: Base styles */
body {
    background: var(--bg-primary);
    transition: background-color 0.2s ease;
}

.main-content {
    min-height: 100vh;
}

/* PERFORMANCE: Simplified hero section with mobile-first animations */
.tool-hero {
    margin-top: 0;
    padding: 120px 0 80px;
    position: relative;
    z-index: 2;
    background: linear-gradient(135deg, var(--bg-primary) 0%, rgba(59, 130, 246, 0.1) 30%, rgba(16, 185, 129, 0.1) 70%, var(--bg-primary) 100%);
}
/* PERFORMANCE: Mobile-optimized hero animations - disabled on smaller screens */
@media (min-width: 768px) {
    .tool-hero::before {
        content: '';
        position: absolute;
        top: 0;
        left: 0;
        right: 0;
        bottom: 0;
        background: 
            radial-gradient(circle at 20% 80%, rgba(59, 130, 246, 0.1) 0%, transparent 50%),
            radial-gradient(circle at 80% 20%, rgba(16, 185, 129, 0.1) 0%, transparent 50%);
        animation: heroBackgroundPulse 8s ease-in-out infinite;
    }
}

@keyframes heroBackgroundPulse {
    0%, 100% { opacity: 0.6; }
    50% { opacity: 1; }
}

.hero-content {
    text-align: center;
    max-width: 800px;
    margin: 0 auto;
    position: relative;
    z-index: 3;
}

.hero-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100px;
    height: 100px;
    margin: 0 auto 30px auto;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 50%, var(--accent-color) 100%);
    border-radius: 50%;
    box-shadow: 0 15px 35px rgba(59, 130, 246, 0.4);
}


.hero-icon i {
    font-size: 3rem;
    color: white;
    text-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
}

.hero-content h1 {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--text-color);
    margin: 0 0 20px 0;
    line-height: 1.1;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 50%, var(--accent-color) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-content p {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin: 0;
    line-height: 1.6;
    max-width: 600px;
    margin: 0 auto;
}

/* PERFORMANCE: Calculator section optimized */
.calculator-main {
    padding: 60px 0 80px;
    background: var(--bg-primary);
}

.calculator-container {
    max-width: 1200px;
    margin: 0 auto;
}

/* PERFORMANCE: Optimized tab styles */
.calculator-tabs {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 8px;
    margin-bottom: 30px;
    padding: 0 20px;
}

.tab-button {
    padding: 12px 20px;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    color: var(--text-secondary);
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    white-space: nowrap;
    font-size: 0.9rem;
    /* PERFORMANCE: Minimum touch target size for mobile */
    min-height: 44px;
    min-width: 44px;
}

.tab-button:hover {
    border-color: var(--primary-color);
    background: rgba(59, 130, 246, 0.05);
    color: var(--primary-color);
}

.tab-button.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    box-shadow: var(--shadow-lg);
}

/* PERFORMANCE: Calculator card styles */
.calculator-card {
    background: var(--bg-primary);
    border-radius: var(--radius-2xl);
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border-color);
    margin-bottom: 30px;
}

.calculator-display {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    padding: 30px;
    text-align: center;
    color: white;
}

.display-result {
    display: flex;
    align-items: baseline;
    justify-content: center;
    gap: 8px;
    margin-bottom: 10px;
}

.result-value {
    font-size: 3rem;
    font-weight: 800;
    line-height: 1;
}

.result-unit {
    font-size: 1.5rem;
    font-weight: 600;
    opacity: 0.9;
}

.display-formula {
    font-size: 1.1rem;
    opacity: 0.9;
    font-weight: 500;
}

/* PERFORMANCE: Input sections */
.calculator-inputs {
    padding: 30px;
}

.input-section {
    display: none;
}

.input-section.active {
    display: block;
}

.date-inputs {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-bottom: 25px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.input-group label {
    font-weight: 600;
    color: var(--text-color);
    font-size: 0.95rem;
}

.date-input,
.input-group input,
.input-group select {
    padding: 12px 16px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    background: var(--bg-primary);
    color: var(--text-color);
    font-size: 1rem;
    transition: border-color 0.2s ease;
    /* PERFORMANCE: Minimum touch target for mobile */
    min-height: 44px;
}

.date-input:focus,
.input-group input:focus,
.input-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.date-helper {
    margin-top: 5px;
    padding: 8px 12px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-base);
    color: var(--text-secondary);
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.2s ease;
    /* PERFORMANCE: Minimum touch target */
    min-height: 44px;
}

.date-helper:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* PERFORMANCE: Options and checkboxes */
.options-group {
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.checkbox-container {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 15px;
    cursor: pointer;
    font-weight: 500;
    color: var(--text-color);
    /* PERFORMANCE: Minimum touch target */
    min-height: 44px;
}

.checkbox-container input[type="checkbox"] {
    display: none;
}

.checkmark {
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-base);
    background: var(--bg-primary);
    position: relative;
    transition: all 0.2s ease;
}

.checkbox-container input[type="checkbox"]:checked + .checkmark {
    background: var(--primary-color);
    border-color: var(--primary-color);
}

.checkbox-container input[type="checkbox"]:checked + .checkmark::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 6px;
    height: 10px;
    border: solid white;
    border-width: 0 2px 2px 0;
    transform: translate(-50%, -60%) rotate(45deg);
}

/* PERFORMANCE: Working days selector */
.working-days-selector label {
    font-weight: 600;
    color: var(--text-color);
    margin-bottom: 10px;
    display: block;
}

.day-checkboxes {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.day-checkbox {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 8px 12px;
    background: var(--bg-tertiary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 0.9rem;
    font-weight: 500;
    /* PERFORMANCE: Minimum touch target */
    min-height: 44px;
}

.day-checkbox input[type="checkbox"] {
    display: none;
}

.day-checkbox:has(input[type="checkbox"]:checked) {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

/* PERFORMANCE: Action buttons */
.calculator-actions {
    padding: 0 30px 30px;
    display: flex;
    gap: 15px;
    justify-content: center;
}

.btn-calculate,
.btn-clear {
    padding: 15px 30px;
    border: none;
    border-radius: var(--radius-lg);
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 10px;
    min-width: 140px;
    justify-content: center;
    /* PERFORMANCE: Minimum touch target */
    min-height: 44px;
}

.btn-calculate {
    background: var(--primary-color);
    color: white;
    box-shadow: var(--shadow-md);
}

.btn-calculate:hover {
    background: var(--accent-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-clear {
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    border: 2px solid var(--border-color);
}

.btn-clear:hover {
    background: var(--danger-color);
    color: white;
    border-color: var(--danger-color);
}

/* PERFORMANCE: Calendar optimization */
.calendar-container {
    background: var(--bg-primary);
    border-radius: var(--radius-2xl);
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border-color);
    padding: 30px;
    margin-bottom: 30px;
}

.calendar-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
}

.calendar-nav {
    width: 44px; /* PERFORMANCE: Minimum touch target */
    height: 44px;
    border: none;
    background: var(--bg-tertiary);
    border-radius: 50%;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.calendar-nav:hover {
    background: var(--primary-color);
    color: white;
}

.calendar-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-color);
    margin: 0;
}

.calendar-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 1px;
    background: var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.calendar-day-header {
    background: var(--bg-tertiary);
    padding: 12px 8px;
    text-align: center;
    font-weight: 600;
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.calendar-day {
    background: var(--bg-primary);
    padding: 12px 8px;
    text-align: center;
    cursor: pointer;
    transition: background-color 0.2s ease;
    position: relative;
    min-height: 44px; /* PERFORMANCE: Minimum touch target */
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 500;
}

.calendar-day:hover {
    background: var(--bg-secondary);
}

.calendar-day.other-month {
    color: var(--text-tertiary);
    background: var(--bg-secondary);
}

.calendar-day.today {
    background: var(--calendar-today);
    color: white;
    font-weight: 700;
}

.calendar-day.start-date {
    background: var(--secondary-color);
    color: white;
    font-weight: 700;
}

.calendar-day.end-date {
    background: var(--primary-color);
    color: white;
    font-weight: 700;
}

.calendar-day.in-range {
    background: var(--calendar-range);
    color: var(--primary-color);
}

.calendar-day.weekend {
    background: rgba(245, 158, 11, 0.1);
    color: var(--warning-color);
}

.calendar-day.holiday {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger-color);
    font-weight: 600;
}

.calendar-legend {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.legend-color {
    width: 16px;
    height: 16px;
    border-radius: 50%;
}

.legend-color.start-date { background: var(--secondary-color); }
.legend-color.end-date { background: var(--primary-color); }
.legend-color.weekend { background: var(--warning-color); }
.legend-color.holiday { background: var(--danger-color); }

/* PERFORMANCE: Results section */
.results-details {
    background: var(--bg-primary);
    border-radius: var(--radius-2xl);
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border-color);
    padding: 30px;
    display: none;
}

.results-details.active {
    display: block;
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
}

.result-item {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
}

.result-label {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

.result-value-large {
    font-size: 2rem;
    font-weight: 800;
    color: var(--primary-color);
    margin-bottom: 5px;
}

/* PERFORMANCE: Holiday and recurring results */
.holiday-list,
.recurring-results {
    max-height: 400px;
    overflow-y: auto;
    margin-top: 20px;
}

.holiday-item,
.recurring-date {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    margin-bottom: 10px;
    border: 1px solid var(--border-color);
    /* PERFORMANCE: Minimum touch target */
    min-height: 44px;
}

.holiday-name {
    font-weight: 600;
    color: var(--text-color);
}

.holiday-date {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.recurring-date {
    font-weight: 500;
    color: var(--text-color);
    justify-content: flex-start;
}

/* PERFORMANCE: Format results */
.format-results {
    margin-top: 20px;
}

.format-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    margin-bottom: 10px;
    border: 1px solid var(--border-color);
    /* PERFORMANCE: Minimum touch target */
    min-height: 44px;
}

.format-label {
    font-weight: 600;
    color: var(--text-secondary);
}

.format-value {
    font-family: monospace;
    color: var(--text-color);
    background: var(--bg-tertiary);
    padding: 4px 8px;
    border-radius: var(--radius-base);
}

/* PERFORMANCE: Mobile-first responsive design */
@media (max-width: 768px) {
    .hero-content h1 {
        font-size: 2rem;
    }
    
    .calculator-tabs {
        flex-direction: column;
        align-items: center;
    }
    
    .tab-button {
        width: 100%;
        max-width: 300px;
    }
    
    .date-inputs {
        grid-template-columns: 1fr;
    }
    
    .calculator-actions {
        flex-direction: column;
        align-items: center;
    }
    
    .btn-calculate,
    .btn-clear {
        width: 100%;
        max-width: 300px;
    }
    
    .calendar-day {
        min-height: 40px;
        padding: 8px 4px;
    }
    
    .results-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .tool-hero {
        padding: 100px 0 60px;
    }
    
    .hero-icon {
        width: 80px;
        height: 80px;
    }
    
    .hero-icon i {
        font-size: 2.5rem;
    }
    
    .calculator-card,
    .calendar-container {
        margin: 0 10px 20px;
    }
    
    .calculator-inputs {
        padding: 20px;
    }
    
    .result-value {
        font-size: 2.5rem;
    }
}

/* PERFORMANCE: Reduce motion for users who prefer it */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}


