style.css

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

body {
    text-align: center;
    font-family: 'Roboto', sans-serif;
    background-color: #ddd;
}

h1 {
    color: #1769aa;
}

.container {
    margin: 1rem auto;
    padding: 1rem;
    width: 80%;
    border-radius: 5px;
    background-color: white;
    box-shadow: 1px 1px 6px 5px #bbb;
}

.container>div {
    display: flex;
    justify-content: space-around;
}

.exampleDiv {
    margin-top: 1rem;
    text-align: left;
}

.example {
    background-color: #ddd;
    border: 1px solid #eee;
    border-radius: 5px;
    margin-top: 0.5rem;
    padding: 0.5rem;
}

ul {
    margin-left: 1.5rem;
}

.sliderCont{
    display: flex;
    align-items: center;
}
.sliderCont>h3{
    margin-right: 0.5rem;
}

.speedSlider{
    color: yellow;
    /* background-color: teal; */
}

.root {
    margin: 1rem auto;
    text-align: center;
    border: 1px solid black;
    width: 350px;
    display: grid;
    grid-template-rows: repeat(9, 0.5fr);
    grid-template-columns: repeat(9, 0.5fr);
}

/* sudoku design */

.root>div {
    padding: 0.5rem;
    border: 1px solid #aaa;
    vertical-align: middle;
    background-color: white;
    /* font-weight: bold; */
}

.root>div:nth-child(3n) {
    border-right: 1px solid black;
}

.root>div:nth-child(9n+1) {
    border-left: 1px solid black;
}

.root>div:nth-child(-n+9) {
    border-top: 1px solid black;
}

.root>div:nth-child(n+73) {
    border-bottom: 1px solid black;
}

.root>div:nth-child(n+19):nth-child(-n+27) {
    border-bottom: 1px solid black;
}

.root>div:nth-child(n+46):nth-child(-n+54) {
    border-bottom: 1px solid black;
}

/* sudoku desing end */

button {
    padding: 0.5rem 2rem;
    background-color: #1769aa;
    border: 0;
    border-radius: 3px;
    color: white;
}

#added, .success {
    background-color: green;
    color: white;
}

#removed, .failed {
    background-color: red;
    color: white;
}

.message {
    color: white;
    border-radius: 5px;
    padding: 0.5rem;
}