style.css

body {
    font-family: "Roboto", sans-serif;
    margin: 0px;
    display: flex;
    background-color: bisque;
    align-items: center;
    justify-content: center;
}
.side-panel {
    display: flex;
    flex-flow: column nowrap;
    margin: 8px;
    align-items: center;
    justify-content: space-between;
    background-color: bisque;
    border: solid black;
    border-radius: 20px;
    width: 550px;
    

}

.title {
    background-color: aquamarine;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0px;
    border-radius:  20px;
    width: 500px;
    height: 150px;
    border: solid;
    border-color: black;
    margin: 8px;
}

.button-container {
    display: flex;
    flex-flow: column nowrap;
    justify-content: space-around;
    
    
    
}

button {
    border-radius: 20px;
    height: 100px;
    width: 200px;
    padding: 20px;
    margin: 10px;
    border-style: solid;
    border-color: black;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;

}

#normal {
    background-color: black;
    color: white;
}

#erase {
    background-color: pink;
}

#rainbow {
    background: linear-gradient(170deg, red,orange,yellow,green,blue,indigo,violet);
    color: white;
    
}


.container {
    display: flex;
    flex-wrap: wrap;
    padding: 0px;
    width: 600px;
    height: 600px;
    margin: 8px;
    background-color: white;
    border: solid black;
}