:root {
    --primary-color: #800000;
    --secondary-color: #D2B48C;
    --success-color: #606060;
    --danger-color: #800000;
    --light-bg: #F5F5F5;
    --light-text: #404040;
    --light-container: #FFFFFF;
    --light-border: #D0D0D0;
    --light-highlight: #F0E6D2;
    --light-table-header: #E8E0D0;
    --max-content-width: 1200px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    line-height: 1.6;
    color: var(--light-text);
    background: var(--light-bg);
    font-size: 1rem;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: var(--max-content-width);
    margin: 0 auto;
    padding: min(20px, 5vw);
    width: 100%;
}

/* Header & Navigation */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid var(--light-border);
    flex-wrap: wrap;
    gap: 15px;
}

.header h1 {
    color: var(--primary-color);
    font-size: clamp(1.5rem, 4vw, 2rem);
    margin: 0;
}

.nav-links {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.nav-links a {
    padding: 12px 16px;
    background: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 8px;
    font-weight: 600;
    transition: all 0.2s ease;
    min-width: 100px;
    text-align: center;
    white-space: nowrap;
}

.nav-links a:hover, .nav-links a:focus {
    background: #600000;
    transform: translateY(-1px);
    outline: none;
}

/* Buttons */
button, .btn-primary, .btn-secondary {
    padding: 14px 20px;
    border: none;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 1rem;
    min-width: 120px;
}

.btn-primary, button:not(.btn-secondary):not(.edit-btn):not(.remove-btn):not(.modal-close) {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover, button:not(.btn-secondary):not(.edit-btn):not(.remove-btn):not(.modal-close):hover {
    background: #600000;
    transform: translateY(-1px);
}

.btn-secondary, .edit-btn, .participant-edit-btn, .participant-action-btn.enable {
    background: var(--secondary-color);
    color: #333;
}

.btn-secondary:hover, .edit-btn:hover, .participant-edit-btn:hover, .participant-action-btn.enable:hover {
    background: #C0A070;
    transform: translateY(-1px);
}

.remove-btn, .participant-action-btn.disable {
    background: var(--danger-color);
    color: white;
}

.remove-btn:hover, .participant-action-btn.disable:hover {
    background: #600000;
    transform: translateY(-1px);
}

/* Forms & Inputs */
input, select {
    padding: 14px;
    border: 2px solid var(--light-border);
    border-radius: 8px;
    font-size: 1rem;
    font-family: inherit;
    transition: border-color 0.2s ease;
    width: 100%;
    box-sizing: border-box;
}

input:focus, select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(128, 0, 0, 0.1);
}

label {
    display: block;
    margin-bottom: 6px;
    font-weight: 600;
    color: var(--primary-color);
    font-size: 0.95rem;
}

/* Cards & Containers */
.create-event, .add-participant, .add-transaction, .transactions-grid, 
.balances-section, .debts-section, .manual-settlement, .event-card, 
.participant-card {
    background: var(--light-container);
    padding: 24px;
    border-radius: 12px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    margin-bottom: 24px;
    border: 1px solid var(--light-border);
}

.event-card, .participant-card {
    transition: all 0.2s ease;
    padding: 20px;
    margin-bottom: 0;
}

.event-card:hover, .participant-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}

.create-event h2, .add-participant h2, .add-transaction h2, 
.transactions-grid h2, .balances-section h2, .debts-section h2, 
.manual-settlement h2 {
    color: var(--primary-color);
    margin-bottom: 16px;
    font-size: 1.4rem;
}

/* Grids */
.events-grid, .participants-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
}

.balances-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 16px;
    margin-top: 16px;
}

.shares-grid, .participants-shares {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 16px;
    margin-top: 12px;
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: 20px;
}

.modal.hidden {
    display: none;
}

.modal-content {
    background: var(--light-container);
    border-radius: 12px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
    max-width: min(600px, 95vw);
    max-height: 90vh;
    overflow-y: auto;
    padding: 24px;
    width: 100%;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--light-border);
}

.modal-close {
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--light-text);
    padding: 8px;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    transition: all 0.2s ease;
}

.modal-close:hover {
    background: var(--light-highlight);
    color: var(--primary-color);
}

.modal-form {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.modal-actions {
    display: flex;
    gap: 12px;
    justify-content: flex-end;
    margin-top: 24px;
    padding-top: 20px;
    border-top: 1px solid var(--light-border);
    flex-wrap: wrap;
}

/* Tables */
.expense-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 16px;
    font-size: 0.95rem;
}

.expense-table th, .expense-table td {
    padding: 12px 8px;
    text-align: left;
    border-bottom: 1px solid var(--light-border);
    vertical-align: middle;
    min-width: 100px;
}

.expense-table th {
    background: var(--light-table-header);
    font-weight: 600;
    color: var(--primary-color);
    position: sticky;
    top: 0;
    z-index: 10;
}

.expense-table tr:hover {
    background: var(--light-highlight);
}

.expense-table button {
    padding: 8px 12px;
    font-size: 0.85rem;
    margin: 2px;
    white-space: nowrap;
    min-width: auto;
}

/* Balance Cards */
.balance-card {
    padding: 20px;
    border-radius: 12px;
    text-align: center;
    border: 2px solid var(--light-border);
    background: var(--light-container);
    transition: transform 0.2s ease;
}

.balance-card:hover {
    transform: translateY(-1px);
}

.balance-card.positive {
    background: var(--light-highlight);
    border-color: var(--secondary-color);
}

.balance-card.negative {
    background: #FFE6E6;
    border-color: var(--danger-color);
}

.balance {
    font-size: 1.4rem;
    font-weight: 700;
    margin-bottom: 5px;
}

.balance-card.positive .balance {
    color: var(--primary-color);
}

.balance-card.negative .balance {
    color: var(--danger-color);
}

/* Debt Items */
.debt-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px;
    border: 1px solid var(--light-border);
    border-radius: 12px;
    margin-bottom: 12px;
    background: var(--light-highlight);
    gap: 16px;
}

.debt-info .amount {
    color: var(--primary-color);
    font-weight: 700;
    font-size: 1.1rem;
}

.settle-form {
    display: flex;
    gap: 10px;
    align-items: center;
    flex-wrap: wrap;
}

.settle-form input {
    width: 120px;
    padding: 10px;
}

.settle-form button {
    padding: 10px 16px;
    font-size: 0.9rem;
    min-width: auto;
    white-space: nowrap;
}

/* Disabled States */
.participant-header.disabled, .expense-table th.disabled, .balance-card.disabled {
    opacity: 0.6;
}

.participant-header.disabled {
    background: var(--light-border) !important;
}

.expense-table th.disabled {
    background: var(--light-border) !important;
    color: var(--light-text) !important;
}

.balance-card.disabled {
    background: var(--light-border) !important;
    border-color: #ccc !important;
}

input:disabled {
    background: var(--light-border);
    color: var(--light-text);
    cursor: not-allowed;
    opacity: 0.7;
}

/* Error States */
.no-participants, .error-page {
    background: var(--light-highlight);
    border: 2px solid var(--secondary-color);
    color: var(--primary-color);
    padding: 24px;
    border-radius: 12px;
    text-align: center;
    font-weight: 600;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .container {
        padding: 16px;
    }
    
    .header {
        flex-direction: column;
        text-align: center;
        gap: 16px;
    }
    
    .nav-links {
        width: 100%;
        flex-direction: column;
    }
    
    .nav-links a {
        width: 100%;
        padding: 16px;
        font-size: 1.1rem;
    }
    
    .create-event form, .add-participant form {
        flex-direction: column;
        gap: 16px;
    }
    
    .events-grid, .participants-grid, .shares-grid, .participants-shares {
        grid-template-columns: 1fr;
    }
    
    .balances-grid {
        grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    }
    
    .modal-content {
        padding: 20px;
        border-radius: 12px 12px 0 0;
        max-height: 95vh;
    }
    
    .modal-actions {
        flex-direction: column;
        gap: 12px;
    }
    
    .modal-actions button, button {
        width: 100%;
        min-width: auto;
        padding: 16px;
        font-size: 1.1rem;
    }
    
    .expense-table {
        font-size: 0.85rem;
        display: block;
        overflow-x: auto;
        white-space: nowrap;
        -webkit-overflow-scrolling: touch;
    }
    
    .expense-table th, .expense-table td {
        padding: 10px 6px;
        min-width: 80px;
    }
    
    .debt-item {
        flex-direction: column;
        gap: 16px;
        align-items: stretch;
    }
    
    .settle-form {
        flex-direction: column;
        gap: 12px;
    }
    
    .settle-form input, .settle-form button {
        width: 100%;
        padding: 12px;
    }
    
    .participant-info {
        flex-direction: column;
        gap: 12px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 12px;
    }
    
    .create-event, .add-participant, .add-transaction,
    .transactions-grid, .balances-section, .debts-section, .manual-settlement {
        padding: 16px;
    }
    
    .balances-grid {
        grid-template-columns: 1fr;
    }
    
    .expense-table {
        font-size: 0.8rem;
    }
    
    .expense-table th, .expense-table td {
        padding: 8px 4px;
        min-width: 70px;
    }
    
    .modal {
        padding: 10px;
        align-items: flex-end;
    }
    
    .modal-content {
        max-height: 90vh;
        border-radius: 16px 16px 0 0;
    }
}

/* Touch devices */
@media (hover: none) and (pointer: coarse) {
    button, .nav-links a, input, select {
        min-height: 44px;
    }
    
    .expense-table button {
        min-width: 44px;
        min-height: 36px;
    }
}