body {
    background-color: #f7f7f7;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    font-size: 16px;
    line-height: 1.5;
    color: #444;
    margin: 5%;
    padding: 0;
}

.header {
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: center;
}

.input-row {
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: center;
}

.option-row {
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: center;
    margin-top: 10px;
}

h1 {
    text-align: center;
    margin-top: auto;
    font-size: 3rem;
    color: #333;
}

label {
    font-size: 1.2rem;
    color: #333;
    text-align: center;
    margin: 5px;
}

.text-input {
    border: 1px solid #ccc;
    box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
    font-size: 1.2rem;
    color: #333;
    background-color: #f5f5f5;
    transition: box-shadow 0.3s ease;
    margin: 10px;
}

.text-input:focus {
    outline: none;
    box-shadow: 0 0 5px rgba(0, 0, 0, 0.5);
}

#target {
    padding: 10px;
    width: 300px;
    border-radius: 5px;
}

#filler-input {
    width: 15px;
    height: 15px;
    border-radius: 2px;
}

.btn {
    width: 150px;
    background-color: #4CAF50;
    color: #fff;
    border: none;
    padding: 10px 20px;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s ease;
    font-size: 1.2rem;
    margin: 10px;
}

.btn:hover {
    background-color: #e74c3c;
}

#canvas {
    margin-top: 30px;
    padding: 50px;
    background-color: #fff;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    border: #333;
    border-radius: 15px;
    min-height: 550px;
    min-width: 550px;
}

.option {
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: center;
    margin-left: 30px;
}

.option-title {
    margin-right: 5px;
}

#flip-cb {
    width: 15px;
    height: 15px;
}