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

/* CSS Custom Properties */
:root {
    /* Color Palette */
    --color-primary: #E4C1F9;
    --color-secondary: #F6DFEB;
    --color-accent: #D0F4DE;
    --color-warning: #FCF6BD;
    --color-danger: #FFB7C5;
    
    /* Derived Colors */
    --color-primary-dark: #d1a3f5;
    --color-primary-light: #f0d9fc;
    --color-text: #2d2d2d;
    --color-text-light: #666;
    --color-text-muted: #999;
    --color-white: #ffffff;
    --color-background: #fafafa;
    --color-border: #e0e0e0;
    --color-shadow: rgba(0, 0, 0, 0.1);
    
    /* Typography */
    --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-size-4xl: 2.5rem;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px var(--color-shadow);
    --shadow-md: 0 4px 6px var(--color-shadow);
    --shadow-lg: 0 10px 15px var(--color-shadow);
    --shadow-xl: 0 20px 25px var(--color-shadow);
    
    /* Transitions */
    --transition-fast: 0.15s ease-in-out;
    --transition-normal: 0.3s ease-in-out;
    --transition-slow: 0.5s ease-in-out;
    
    /* Z-index */
    --z-toast: 1000;
    --z-modal: 900;
    --z-dropdown: 800;
    --z-header: 100;
}

/* Dark Theme Variables */
[data-theme="dark"] {
    --color-text: #e0e0e0;
    --color-text-light: #b0b0b0;
    --color-text-muted: #808080;
    --color-background: #1a1a1a;
    --color-white: #2d2d2d;
    --color-border: #404040;
    --color-shadow: rgba(255, 255, 255, 0.1);
    --color-primary: #b794f6;
    --color-secondary: #e6b3cc;
    --color-accent: #9ae6b4;
    --color-warning: #f6e05e;
    --color-danger: #fc8181;
}

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

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-background);
    transition: background-color var(--transition-normal), color var(--transition-normal);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-md);
    flex: 1;
}

/* Theme Toggle */
.theme-toggle {
    position: fixed;
    top: var(--spacing-md);
    right: var(--spacing-md);
    z-index: var(--z-header);
    background: var(--color-primary);
    border: none;
    border-radius: 50%;
    width: 3rem;
    height: 3rem;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
}

.theme-toggle:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-lg);
}

.theme-toggle__icon {
    font-size: var(--font-size-lg);
    transition: transform var(--transition-normal);
}

.theme-toggle:hover .theme-toggle__icon {
    transform: rotate(180deg);
}

/* Header */
.header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
    padding: var(--spacing-xl) 0;
}

.header__title {
    font-size: var(--font-size-3xl);
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--spacing-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.header__icon {
    font-size: var(--font-size-4xl);
    animation: bounce 2s infinite;
}

.header__subtitle {
    font-size: var(--font-size-lg);
    color: var(--color-text-light);
    max-width: 600px;
    margin: 0 auto;
}

/* Cards */
.card {
    background: var(--color-white);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-md);
    transition: all var(--transition-normal);
    border: 1px solid var(--color-border);
    margin-bottom: var(--spacing-xl);
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.card--highlight {
    background: linear-gradient(135deg, var(--color-primary-light), var(--color-secondary));
    border: 2px solid var(--color-primary);
}

.card__title {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--color-text);
}

.card__icon {
    font-size: var(--font-size-2xl);
}

/* Forms */
.date-form {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.form-label {
    font-weight: 600;
    color: var(--color-text);
    font-size: var(--font-size-base);
}

.form-input {
    padding: var(--spacing-md);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-family: inherit;
    background: var(--color-white);
    color: var(--color-text);
    transition: all var(--transition-normal);
}

.form-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(228, 193, 249, 0.2);
}

.form-input:invalid {
    border-color: var(--color-danger);
}

.form-help {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-xl);
    border: none;
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-weight: 600;
    font-family: inherit;
    cursor: pointer;
    transition: all var(--transition-normal);
    text-decoration: none;
    min-height: 48px;
}

.btn--primary {
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
    color: var(--color-white);
    box-shadow: var(--shadow-md);
}

.btn--primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn--secondary {
    background: var(--color-white);
    color: var(--color-primary);
    border: 2px solid var(--color-primary);
}

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

.btn__icon {
    font-size: var(--font-size-lg);
}

/* Age Display */
.age-display {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.age-item {
    text-align: center;
    padding: var(--spacing-lg);
    background: var(--color-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    transition: transform var(--transition-normal);
}

.age-item:hover {
    transform: scale(1.05);
}

.age-number {
    display: block;
    font-size: var(--font-size-4xl);
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--spacing-xs);
    animation: countUp 0.8s ease-out;
}

.age-label {
    font-size: var(--font-size-sm);
    color: var(--color-text-light);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-weight: 600;
}

/* Metrics Grid */
.metrics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.metric-card {
    background: var(--color-white);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    box-shadow: var(--shadow-md);
    transition: all var(--transition-normal);
    border: 1px solid var(--color-border);
}

.metric-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.metric-card__icon {
    font-size: var(--font-size-3xl);
    margin-bottom: var(--spacing-md);
}

.metric-card__value {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--spacing-sm);
    animation: countUp 1s ease-out;
}

.metric-card__label {
    font-size: var(--font-size-sm);
    color: var(--color-text-light);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Info Grid */
.info-grid {
    display: grid;
    gap: var(--spacing-md);
}

.info-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
    background: var(--color-background);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
}

.info-label {
    font-weight: 600;
    color: var(--color-text-light);
}

.info-value {
    font-weight: 700;
    color: var(--color-primary);
}

/* Share Buttons */
.share-buttons {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

/* Instructions */
.instructions {
    margin-top: var(--spacing-2xl);
}

.instructions-list {
    list-style: none;
    counter-reset: step-counter;
}

.instructions-list li {
    counter-increment: step-counter;
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    background: var(--color-background);
    border-radius: var(--radius-md);
    border-left: 4px solid var(--color-primary);
    position: relative;
    padding-left: var(--spacing-2xl);
}

.instructions-list li::before {
    content: counter(step-counter);
    position: absolute;
    left: var(--spacing-md);
    top: 50%;
    transform: translateY(-50%);
    background: var(--color-primary);
    color: var(--color-white);
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: var(--font-size-sm);
    font-weight: 700;
}

/* Error Message */
.error-message {
    background: var(--color-danger);
    color: var(--color-white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    margin: var(--spacing-lg) 0;
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    animation: slideIn 0.3s ease-out;
}

.error-message__icon {
    font-size: var(--font-size-xl);
}

/* Loading Spinner */
.loading-spinner {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: var(--z-modal);
    color: var(--color-white);
}

.spinner {
    width: 40px;
    height: 40px;
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top: 4px solid var(--color-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: var(--spacing-md);
}

/* Toast Notification */
.toast {
    position: fixed;
    bottom: var(--spacing-md);
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--color-white);
    color: var(--color-text);
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    z-index: var(--z-toast);
    transition: transform var(--transition-normal);
    border: 1px solid var(--color-border);
}

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

.toast__icon {
    font-size: var(--font-size-lg);
}

/* Footer */
.footer {
    background: var(--color-white);
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-xl) 0;
    margin-top: var(--spacing-3xl);
}

.footer__content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    text-align: center;
}

.footer__text {
    color: var(--color-text-light);
    font-size: var(--font-size-sm);
}

.footer__link {
    color: var(--color-primary);
    text-decoration: none;
    font-weight: 600;
    transition: color var(--transition-normal);
}

.footer__link:hover {
    color: var(--color-primary-dark);
    text-decoration: underline;
}

/* Animations */
@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateY(0);
    }
    40% {
        transform: translateY(-10px);
    }
    60% {
        transform: translateY(-5px);
    }
}

@keyframes countUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: var(--spacing-sm);
    }
    
    .header__title {
        font-size: var(--font-size-2xl);
        flex-direction: column;
        gap: var(--spacing-xs);
    }
    
    .header__icon {
        font-size: var(--font-size-3xl);
    }
    
    .card {
        padding: var(--spacing-lg);
        margin-bottom: var(--spacing-lg);
    }
    
    .age-display {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }
    
    .metrics-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-md);
    }
    
    .share-buttons {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
    
    .info-item {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-xs);
    }
    
    .theme-toggle {
        top: var(--spacing-sm);
        right: var(--spacing-sm);
        width: 2.5rem;
        height: 2.5rem;
    }
}

@media (max-width: 480px) {
    .metrics-grid {
        grid-template-columns: 1fr;
    }
    
    .age-number {
        font-size: var(--font-size-3xl);
    }
    
    .metric-card__value {
        font-size: var(--font-size-xl);
    }
    
    .instructions-list li {
        padding-left: var(--spacing-xl);
    }
}

/* High Contrast Mode */
@media (prefers-contrast: high) {
    :root {
        --color-border: #000000;
        --color-shadow: rgba(0, 0, 0, 0.3);
    }
    
    .card {
        border-width: 2px;
    }
    
    .btn {
        border-width: 2px;
    }
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
    
    .header__icon {
        animation: none;
    }
}

/* Print Styles */
@media print {
    .theme-toggle,
    .share-buttons,
    .footer {
        display: none;
    }
    
    .container {
        max-width: none;
        padding: 0;
    }
    
    .card {
        box-shadow: none;
        border: 1px solid #000;
        page-break-inside: avoid;
    }
}

/* Focus Styles for Accessibility */
.btn:focus,
.form-input:focus,
.theme-toggle:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Utility Classes */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

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

.hidden {
    display: none !important;
}

.fade-in {
    animation: fadeIn 0.5s ease-out;
}