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

:root {
    --primary-color: #4f46e5;
    --primary-dark: #4338ca;
    --success-color: #10b981;
    --error-color: #ef4444;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #f9fafb;
    --bg-secondary: #ffffff;
    --border-color: #e5e7eb;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #0ea5e9 0%, #06b6d4 100%);
    min-height: 100vh;
    color: var(--text-primary);
    line-height: 1.6;
    padding: 1rem;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: 600px;
    margin: 0 auto;
}

/* Utility Classes */
.hidden {
    display: none !important;
}

/* Header */
header {
    margin-bottom: 2rem;
    color: white;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
}

.header-content > div:first-child {
    text-align: center;
    flex: 1;
}

.header-buttons {
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

header h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

.subtitle {
    font-size: 1rem;
    opacity: 0.9;
}

/* Status Messages */
.status {
    padding: 1rem;
    border-radius: 0.5rem;
    margin-bottom: 1rem;
    font-weight: 500;
    animation: slideDown 0.3s ease;
}

.status.success {
    background-color: var(--success-color);
    color: white;
}

.status.error {
    background-color: var(--error-color);
    color: white;
}

.status.hidden {
    display: none;
}

/* Cards */
.card {
    background: var(--bg-secondary);
    border-radius: 1rem;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow-lg);
}

.card h2 {
    font-size: 1.25rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.section-header h2 {
    margin-bottom: 0;
}

/* Form Styles */
.form-group {
    margin-bottom: 1.25rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
    font-size: 0.875rem;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 0.5rem;
    font-size: 1rem;
    transition: all 0.2s;
    background: white;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.form-help {
    display: block;
    margin-top: 0.5rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

/* Buttons */
.btn {
    width: 100%;
    padding: 0.875rem;
    border: none;
    border-radius: 0.5rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

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

.btn-primary:hover:not(:disabled) {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-lg);
}

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

.btn-primary:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.btn-icon {
    background: transparent;
    border: none;
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0.25rem;
    transition: transform 0.2s;
}

.btn-icon:hover {
    transform: scale(1.1);
}

.btn-icon:active {
    transform: scale(0.95);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    border: 2px solid white;
    padding: 0.5rem 1rem;
    width: auto;
    font-size: 0.9rem;
}

.btn-secondary:hover:not(:disabled) {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-1px);
}

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

/* Login Screen */
.login-screen {
    max-width: 400px;
    margin: 4rem auto;
    min-height: 400px;
}

.login-screen h2 {
    text-align: center;
    margin-bottom: 0.5rem;
    font-size: 1.75rem;
}

.login-subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-size: 0.95rem;
}

/* User Info */
.user-info {
    background: var(--bg-primary);
    padding: 1rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
}

.user-info p {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
    font-size: 0.9rem;
}

.user-info p:last-child {
    margin-bottom: 0;
}

/* Balances */
.balances-summary {
    min-height: 100px;
}

.balance-section {
    margin-bottom: 1.5rem;
}

.balance-section:last-child {
    margin-bottom: 0;
}

.balance-section h3 {
    font-size: 1rem;
    margin-bottom: 0.75rem;
    color: var(--text-secondary);
    font-weight: 600;
}

.balance-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    background: var(--bg-primary);
    border-radius: 0.5rem;
    margin-bottom: 0.5rem;
}

.balance-item:last-child {
    margin-bottom: 0;
}

.balance-user {
    font-weight: 600;
    color: var(--text-primary);
}

.balance-amount {
    font-weight: 700;
    font-size: 1.1rem;
}

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

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

.no-balances {
    text-align: center;
    padding: 2rem;
    color: var(--text-secondary);
}

/* Spinner */
.spinner {
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

.spinner.hidden {
    display: none;
}

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

/* Payments List */
.payments-list {
    max-height: 500px;
    overflow-y: auto;
}

.payment-item {
    padding: 1rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background 0.2s;
}

.payment-item:last-child {
    border-bottom: none;
}

.payment-item:hover {
    background: var(--bg-primary);
}

.payment-info {
    flex: 1;
}

.payment-description {
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.payment-meta {
    font-size: 0.875rem;
    color: var(--text-secondary);
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.payment-category {
    display: inline-block;
    padding: 0.125rem 0.5rem;
    background: var(--bg-primary);
    border-radius: 0.25rem;
    font-size: 0.75rem;
    text-transform: capitalize;
}

.payment-right {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.payment-amount {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
    white-space: nowrap;
}

.btn-delete {
    background: transparent;
    border: none;
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0.5rem;
    opacity: 0.6;
    transition: all 0.2s;
    border-radius: 0.375rem;
}

.btn-delete:hover {
    opacity: 1;
    background: rgba(239, 68, 68, 0.1);
    transform: scale(1.1);
}

.btn-delete:active {
    transform: scale(0.95);
}

.loading {
    text-align: center;
    padding: 2rem;
    color: var(--text-secondary);
}

.empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-secondary);
}

.empty-state-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

/* Footer */
footer {
    text-align: center;
    margin-top: 2rem;
    color: white;
    opacity: 0.8;
    font-size: 0.875rem;
}

/* Animations */
@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Responsive Design */
@media (max-width: 480px) {
    body {
        padding: 0.5rem;
    }

    header h1 {
        font-size: 1.5rem;
    }

    .card {
        padding: 1rem;
        border-radius: 0.75rem;
    }

    .payment-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }

    .payment-right {
        align-self: stretch;
        justify-content: space-between;
        width: 100%;
    }
}

/* Landscape mode for mobile */
@media (max-height: 600px) and (orientation: landscape) {
    header {
        margin-bottom: 1rem;
    }

    header h1 {
        font-size: 1.5rem;
    }

    .card {
        padding: 1rem;
    }

    .payments-list {
        max-height: 200px;
    }
}

/* Touch-friendly tap targets */
@media (hover: none) and (pointer: coarse) {
    .btn,
    .btn-icon,
    .form-group input,
    .form-group select {
        min-height: 44px;
    }
}