/* CSS Variables for theming */
:root {
    /* Light mode colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --accent-color: #3b82f6;
    --accent-hover: #2563eb;
    --success-color: #10b981;
    --error-color: #ef4444;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
}

/* Dark mode colors */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #64748b;
    --border-color: #334155;
    --accent-color: #60a5fa;
    --accent-hover: #3b82f6;
    --success-color: #34d399;
    --error-color: #f87171;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.3), 0 2px 4px -2px rgb(0 0 0 / 0.3);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.3), 0 4px 6px -4px rgb(0 0 0 / 0.3);
}

/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    width: 100%;
    max-width: 100%;
    overflow-x: hidden;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* Container */
.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 1rem;
    min-height: 100vh;
    width: 100%;
    box-sizing: border-box;
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}

h1 {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* Header controls */
.header-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

/* Language selector */
.language-select {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.5rem;
    color: var(--text-primary);
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.language-select:hover {
    background-color: var(--bg-tertiary);
}

.language-select:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgb(59 130 246 / 0.1);
}

/* Theme toggle */
.theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s ease;
    background-color: var(--bg-secondary);
}

.theme-toggle:hover {
    background-color: var(--bg-tertiary);
    transform: scale(1.05);
}

.theme-toggle svg {
    color: var(--text-secondary);
    transition: color 0.2s ease;
}

[data-theme="dark"] .sun-icon,
[data-theme="light"] .moon-icon {
    display: none;
}

/* Main content */
main {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* Section headers */
h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

/* People section */
.people-section {
    background-color: var(--bg-secondary);
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: var(--shadow-sm);
}

/* Person rows */
.person-row {
    display: grid;
    grid-template-columns: 1fr 1fr auto;
    gap: 0.75rem;
    margin-bottom: 1rem;
    align-items: center;
    width: 100%;
    box-sizing: border-box;
}

.person-row:last-of-type {
    margin-bottom: 0;
}

/* Input styles */
.name-input,
.amount-input {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.name-input:focus,
.amount-input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgb(59 130 246 / 0.1);
}

.name-input::placeholder,
.amount-input::placeholder {
    color: var(--text-muted);
}

/* Remove button */
.remove-person {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1.25rem;
    color: var(--text-secondary);
    transition: all 0.2s ease;
    background-color: var(--bg-primary);
}

.remove-person:hover {
    background-color: var(--error-color);
    color: white;
    border-color: var(--error-color);
}

/* Add person button */
.add-person-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    width: 100%;
    padding: 0.875rem;
    background-color: var(--bg-tertiary);
    border: 2px dashed var(--border-color);
    border-radius: 8px;
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    margin-top: 1rem;
}

.add-person-btn:hover {
    background-color: var(--bg-primary);
    border-color: var(--accent-color);
    color: var(--accent-color);
}

.add-person-btn svg {
    transition: transform 0.2s ease;
}

.add-person-btn:hover svg {
    transform: scale(1.1);
}

/* Action buttons container */
.action-buttons {
    display: flex;
    gap: 1rem;
    width: 100%;
    box-sizing: border-box;
}

/* Calculate button */
.calculate-btn {
    flex: 2;
    padding: 1rem;
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 1.125rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: var(--shadow-md);
}

.calculate-btn:hover {
    background-color: var(--accent-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-lg);
}

.calculate-btn:active {
    transform: translateY(0);
}

/* Clear button */
.clear-btn {
    flex: 1;
    padding: 1rem;
    background-color: var(--bg-tertiary);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    font-size: 1.125rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: var(--shadow-sm);
}

.clear-btn:hover {
    background-color: var(--error-color);
    color: white;
    border-color: var(--error-color);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.clear-btn:active {
    transform: translateY(0);
}

/* Results section */
.results {
    background-color: var(--bg-secondary);
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
}

.results.hidden {
    display: none;
}

.results h2 {
    margin-bottom: 1.5rem;
}

/* Result cards */
.result-card {
    background-color: var(--bg-primary);
    border-radius: 8px;
    padding: 1.25rem;
    margin-bottom: 1rem;
    box-shadow: var(--shadow-sm);
}

.result-card:last-child {
    margin-bottom: 0;
}

.result-card h3 {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.grand-total,
.per-person {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* Payments list */
.payments-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.payment-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    background-color: var(--bg-secondary);
    border-radius: 6px;
    border-left: 4px solid var(--accent-color);
}

.payment-item.negative {
    border-left-color: var(--error-color);
}

.payment-item.positive {
    border-left-color: var(--success-color);
}

.payment-details {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.payment-from {
    font-weight: 500;
    color: var(--text-primary);
}

.payment-to {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.payment-amount {
    font-weight: 600;
    font-size: 1.125rem;
}

.payment-amount.negative {
    color: var(--error-color);
}

.payment-amount.positive {
    color: var(--success-color);
}

/* Share buttons */
.share-buttons {
    display: flex;
    gap: 1rem;
    margin-top: 1.5rem;
}

.share-buttons .share-btn {
    flex: 1;
}

.mobile-only {
    display: none;
}

@media (max-width: 768px) {
    .mobile-only {
        display: flex;
    }
}

/* Share button */
.share-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    width: 100%;
    padding: 1rem;
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 1.125rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

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

.share-btn:active {
    transform: translateY(0);
}

.share-btn svg {
    transition: transform 0.2s ease;
}

.share-btn:hover svg {
    transform: translateY(-2px);
}

/* Disclaimer */
.disclaimer {
    margin-top: 1.5rem;
    padding: 1rem;
    background-color: var(--bg-tertiary);
    border-radius: 8px;
    border-left: 4px solid #f59e0b;
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
}

.disclaimer .alert-icon {
    color: #f59e0b;
    flex-shrink: 0;
    margin-top: 0.125rem;
}

.disclaimer p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin: 0;
    line-height: 1.5;
    font-weight: 500;
}

/* Responsive design */
@media (max-width: 480px) {
    .container {
        padding: 0.5rem;
        max-width: 100vw;
        overflow-x: hidden;
    }
    
    h1 {
        font-size: 1.5rem;
    }
    
    h2 {
        font-size: 1.25rem;
    }
    
    .people-section,
    .results {
        padding: 0.75rem;
    }
    
    .name-input,
    .amount-input {
        font-size: 0.75rem;
        padding: 0.4rem 0.3rem;
    }
    
    .person-row {
        grid-template-columns: 1fr 1fr auto;
        gap: 0.3rem;
        min-width: 0;
    }
    
    .remove-person {
        width: 32px;
        height: 32px;
        border-radius: 50%;
    }
    
    .grand-total,
    .per-person {
        font-size: 1.5rem;
    }
    
    .payment-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }
    
    .payment-amount {
        align-self: flex-end;
    }
    
    .action-buttons {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .calculate-btn,
    .clear-btn {
        flex: none;
    }
    
    .disclaimer {
        padding: 0.75rem;
        gap: 0.5rem;
    }
    
    .disclaimer .alert-icon {
        width: 14px;
        height: 14px;
    }
}

@media (min-width: 481px) and (max-width: 768px) {
    .person-row {
        grid-template-columns: 2fr 1fr auto;
    }
}

/* Animation for results */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.results:not(.hidden) {
    animation: fadeInUp 0.3s ease-out;
}

/* Focus styles for accessibility */
button:focus-visible,
input:focus-visible {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

/* Smooth scrolling */
html {
    scroll-behavior: smooth;
}