/**
 * USL Anonymous ID - Stylesheet
 * Version: 1.0.0
 * License: MIT
 * 
 * Design Principles:
 * - Mobile-first responsive design
 * - High contrast for accessibility
 * - Minimal dependencies (no external fonts)
 * - System font stack for performance
 */

/* ========================================
   CSS Variables (Design Tokens)
   ======================================== */

:root {
    /* Colors */
    --color-primary: #1a73e8;
    --color-primary-dark: #0d47a1;
    --color-primary-light: #4285f4;
    --color-secondary: #5f6368;
    --color-danger: #d93025;
    --color-danger-dark: #b71c1c;
    --color-success: #1e8e3e;
    --color-warning: #f9ab00;
    
    /* Background & Surface */
    --color-background: #ffffff;
    --color-surface: #f8f9fa;
    --color-surface-elevated: #ffffff;
    
    /* Text */
    --color-text-primary: #202124;
    --color-text-secondary: #5f6368;
    --color-text-disabled: #9aa0a6;
    --color-text-inverse: #ffffff;
    
    /* Borders */
    --color-border: #dadce0;
    --color-border-focus: #1a73e8;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 2px 6px rgba(0, 0, 0, 0.15);
    --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.15);
    --shadow-xl: 0 8px 24px rgba(0, 0, 0, 0.2);
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 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;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
    
    /* Z-index layers */
    --z-base: 0;
    --z-dropdown: 100;
    --z-sticky: 200;
    --z-modal-backdrop: 300;
    --z-modal: 400;
    --z-tooltip: 500;
}

/* ========================================
   Reset & Base Styles
   ======================================== */

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

html {
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.5;
    color: var(--color-text-primary);
    background-color: var(--color-background);
    min-height: 100vh;
    overflow-x: hidden;
}

/* Remove default styling */
button,
input,
select,
textarea {
    font-family: inherit;
    font-size: inherit;
    line-height: inherit;
}

button {
    cursor: pointer;
    border: none;
    background: none;
}

a {
    color: var(--color-primary);
    text-decoration: none;
}

/* ========================================
   App Container
   ======================================== */

#app {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ========================================
   Screen Styles
   ======================================== */

.screen {
    display: none;
    min-height: 100vh;
    flex-direction: column;
}

.screen.active {
    display: flex;
}

.screen-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    padding: var(--spacing-lg);
    max-width: 480px;
    margin: 0 auto;
    width: 100%;
}

.screen-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.screen-header h1 {
    font-size: var(--font-size-xl);
    font-weight: 600;
}

/* ========================================
   Loading Screen
   ======================================== */

#screen-loading {
    justify-content: center;
    align-items: center;
}

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

.loading-spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto var(--spacing-md);
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* ========================================
   Typography
   ======================================== */

h1 {
    font-size: var(--font-size-2xl);
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-sm);
}

h2 {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-sm);
}

p {
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
}

/* ========================================
   Buttons
   ======================================== */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: var(--font-size-base);
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    min-height: 44px;
    min-width: 44px;
}

.btn:focus-visible {
    outline: 2px solid var(--color-border-focus);
    outline-offset: 2px;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

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

.btn-primary:hover:not(:disabled) {
    background-color: var(--color-primary-dark);
}

.btn-primary:active:not(:disabled) {
    background-color: var(--color-primary-dark);
    transform: scale(0.98);
}

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

.btn-secondary:hover:not(:disabled) {
    background-color: var(--color-border);
}

.btn-danger {
    background-color: var(--color-danger);
    color: var(--color-text-inverse);
}

.btn-danger:hover:not(:disabled) {
    background-color: var(--color-danger-dark);
}

.btn-icon {
    padding: var(--spacing-sm);
    border-radius: var(--radius-full);
    background-color: transparent;
    color: var(--color-text-secondary);
}

.btn-icon:hover:not(:disabled) {
    background-color: var(--color-surface);
    color: var(--color-text-primary);
}

.btn-large {
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: var(--font-size-lg);
    min-height: 56px;
    width: 100%;
    background-color: var(--color-surface);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
}

.btn-large:hover:not(:disabled) {
    border-color: var(--color-primary);
    background-color: var(--color-surface-elevated);
    box-shadow: var(--shadow-md);
}

.btn-large:active:not(:disabled) {
    transform: scale(0.98);
}

.btn-full {
    width: 100%;
}

.button-group {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.button-group .btn {
    flex: 1;
}

/* ========================================
   Language Selection
   ======================================== */

.language-options {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    margin-top: var(--spacing-xl);
}

.lang-label {
    font-weight: 500;
}

/* ========================================
   Allergy Selection
   ======================================== */

.allergy-options {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.allergy-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md);
    background-color: var(--color-surface);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.allergy-item:hover {
    border-color: var(--color-primary-light);
}

.allergy-item.selected {
    border-color: var(--color-primary);
    background-color: rgba(26, 115, 232, 0.1);
}

.allergy-item input[type="checkbox"] {
    width: 20px;
    height: 20px;
    accent-color: var(--color-primary);
}

.allergy-item label {
    flex: 1;
    cursor: pointer;
    font-size: var(--font-size-sm);
}

/* ========================================
   QR Code Display
   ======================================== */

.qr-container {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: var(--spacing-xl);
    margin: var(--spacing-lg) 0;
    background-color: var(--color-surface-elevated);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
}

#qr-code {
    display: flex;
    justify-content: center;
    align-items: center;
}

#qr-code canvas,
#qr-code img {
    max-width: 256px;
    max-height: 256px;
    width: 100%;
    height: auto;
}

.id-display {
    text-align: center;
    font-family: monospace;
    font-size: var(--font-size-xs);
    color: var(--color-text-disabled);
    word-break: break-all;
    padding: var(--spacing-sm);
    background-color: var(--color-surface);
    border-radius: var(--radius-sm);
}

.main-actions {
    display: flex;
    justify-content: center;
    margin-top: var(--spacing-xl);
}

/* ========================================
   Settings Screen
   ======================================== */

.settings-section {
    padding: var(--spacing-lg) 0;
    border-bottom: 1px solid var(--color-border);
}

.settings-section:last-child {
    border-bottom: none;
}

.settings-section h2 {
    font-size: var(--font-size-sm);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
}

.setting-item {
    margin-bottom: var(--spacing-md);
}

.settings-danger {
    background-color: rgba(217, 48, 37, 0.05);
    margin: var(--spacing-md) calc(var(--spacing-lg) * -1);
    padding-left: var(--spacing-lg);
    padding-right: var(--spacing-lg);
    border-radius: var(--radius-md);
}

.settings-danger p {
    color: var(--color-danger);
    font-size: var(--font-size-sm);
}

.settings-info {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
}

.settings-info p {
    margin-bottom: var(--spacing-xs);
}

/* ========================================
   Form Elements
   ======================================== */

.select-input {
    width: 100%;
    padding: var(--spacing-md);
    font-size: var(--font-size-base);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-surface-elevated);
    color: var(--color-text-primary);
    cursor: pointer;
    transition: border-color var(--transition-fast);
}

.select-input:focus {
    outline: none;
    border-color: var(--color-border-focus);
}

/* ========================================
   Modal
   ======================================== */

.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: var(--z-modal);
}

.modal.active {
    display: flex;
    justify-content: center;
    align-items: center;
}

.modal-backdrop {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: var(--z-modal-backdrop);
}

.modal-content {
    position: relative;
    z-index: var(--z-modal);
    background-color: var(--color-surface-elevated);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    margin: var(--spacing-lg);
    max-width: 400px;
    width: 100%;
    box-shadow: var(--shadow-xl);
    animation: modalIn var(--transition-normal);
}

@keyframes modalIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.modal-content h2 {
    font-size: var(--font-size-xl);
    margin-bottom: var(--spacing-md);
}

.modal-content p {
    margin-bottom: var(--spacing-lg);
}

.modal-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: flex-end;
}

.modal-actions .btn {
    min-width: 100px;
}

/* Modal allergy options */
.modal-content .allergy-options {
    max-height: 300px;
    overflow-y: auto;
    margin-bottom: var(--spacing-lg);
}

/* ========================================
   Utility Classes
   ======================================== */

.visually-hidden {
    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;
}

.text-danger {
    color: var(--color-danger);
}

.text-success {
    color: var(--color-success);
}

/* ========================================
   Responsive Design
   ======================================== */

@media (min-width: 480px) {
    .allergy-options {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (min-width: 768px) {
    .screen-content {
        padding: var(--spacing-xl);
    }
    
    h1 {
        font-size: var(--font-size-3xl);
    }
}

/* ========================================
   Print Styles (hide UI, show QR)
   ======================================== */

@media print {
    .screen:not(#screen-main) {
        display: none !important;
    }
    
    #screen-main {
        display: flex !important;
    }
    
    .main-actions,
    .btn {
        display: none !important;
    }
    
    .qr-container {
        box-shadow: none;
        border: 1px solid #000;
    }
}

/* ========================================
   Reduced Motion
   ======================================== */

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ========================================
   Dark Mode Support (optional, future)
   ======================================== */

@media (prefers-color-scheme: dark) {
    /* Dark mode variables can be added here in future */
    /* Currently keeping light mode only for MVP */
}