body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
    background-color: #f5f5f5;
}

.container {
    background: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    margin: 0 auto;
    width: 95%;
    max-width: 1200px;
}

.header {
    background: #2c3e50;
    color: white;
    padding: 20px;
    margin: -20px -20px 20px -20px;
    border-radius: 8px 8px 0 0;
}

.btn {
    padding: 8px 16px;
    border: none;
    border-radius: 4px;
    background: #3498db;
    color: white;
    cursor: pointer;
    transition: background 0.3s;
}

.btn:hover {
    background: #2980b9;
}

input[type="text"],
input[type="number"],
select {
    padding: 8px;
    margin: 5px 0;
    border: 1px solid #ddd;
    border-radius: 4px;
    width: 100%;
    max-width: 300px;
}

.expense-table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
    overflow-x: auto;
    display: block;
}

.expense-table th,
.expense-table td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #ddd;
}

.expense-table th {
    background: #f8f9fa;
}

.form-group {
    margin-bottom: 15px;
}

.participants-list {
    list-style: none;
    padding: 0;
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.participant-item {
    background: #e1f5fe;
    padding: 8px 16px;
    border-radius: 20px;
}

.participant-checkbox {
    display: flex;
    align-items: center;
    margin: 8px 0;
    padding: 8px;
    background: #f8f9fa;
    border-radius: 4px;
    cursor: pointer;
}

.participant-checkbox input[type="checkbox"] {
    margin-right: 10px;
    width: 20px;
    height: 20px;
}

.participant-checkbox:hover {
    background: #e9ecef;
}

.settlement-list {
    list-style: none;
    padding: 0;
}

.settlement-item {
    padding: 10px;
    margin: 5px 0;
    background: #e8f5e9;
    border-radius: 4px;
}

.section {
    margin: 30px 0;
}

@media (max-width: 768px) {
    body {
        padding: 10px;
    }

    .container {
        padding: 15px;
    }

    .header {
        margin: -15px -15px 15px -15px;
        padding: 15px;
    }

    .participants-list {
        flex-direction: column;
    }

    .participant-item {
        width: 100%;
        box-sizing: border-box;
    }

    .form-group {
        margin-bottom: 20px;
    }

    input[type="text"],
    input[type="number"],
    select {
        width: 100%;
        max-width: none;
        box-sizing: border-box;
    }

    .btn {
        width: 100%;
        margin: 5px 0;
    }
}

.modal {
    display: none;
    position: fixed;
    z-index: 1;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.4);
}

.modal-content {
    background-color: #fefefe;
    margin: 15% auto;
    padding: 20px;
    border: 1px solid #888;
    width: 80%;
    max-width: 500px;
    border-radius: 8px;
}

.modal-buttons {
    display: flex;
    gap: 10px;
    justify-content: flex-end;
    margin-top: 20px;
}

.btn-danger {
    background-color: #dc3545;
}

.btn-danger:hover {
    background-color: #c82333;
}

input[type="datetime-local"] {
    padding: 8px;
    margin: 5px 0;
    border: 1px solid #ddd;
    border-radius: 4px;
    width: 100%;
    max-width: 300px;
}

@media (max-width: 768px) {
    .modal-content {
        width: 95%;
        margin: 10% auto;
    }
    
    input[type="datetime-local"] {
        width: 100%;
        max-width: none;
        box-sizing: border-box;
    }