body {
    font-family: Arial, sans-serif;
    margin: 20px;
    background-color: #f4f4f4;
}

h1 {
    text-align: center;
    color: #333;
}

#calendar {
    max-width: 900px;
    margin: 0 auto;
    background-color: #fff;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

/* Modal/Form Styling */
#activityFormModal {
    display: none; /* ซ่อนไว้ก่อน */
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0,0,0,0.4);
    justify-content: center;
    align-items: center;
}

#activityFormModal h2 {
    text-align: center;
    margin-bottom: 20px;
}

#activityForm {
    background-color: #fff;
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.3);
    max-width: 500px;
    margin: 50px auto; /* จัดกึ่งกลาง */
}

#activityForm label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
}

#activityForm input[type="date"],
#activityForm input[type="text"],
#activityForm textarea {
    width: calc(100% - 20px);
    padding: 10px;
    margin-bottom: 15px;
    border: 1px solid #ddd;
    border-radius: 4px;
}

#activityForm button {
    background-color: #007bff;
    color: white;
    padding: 10px 15px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 16px;
    margin-right: 10px;
}

#activityForm button:hover {
    opacity: 0.9;
}

#activityForm #deleteActivityBtn {
    background-color: #dc3545;
}

#activityForm #cancelActivityBtn {
    background-color: #6c757d;
}