style.css

* {
    box-sizing: border-box; /* takes into account borders as well */
}

.main {
    width: 800px;
    margin: auto;
    position: relative;
}

.btn-start, .btn-clear {
    background-image: linear-gradient(#fa923f, red);
    color: white;
    border: 1px solid #512751;
    border-radius: 15px;
    margin: 5px auto;
    display: inline-block;
    padding: 10px 28px;
}

.btn-clear {
    background-color: grey;
    color: white;
    border: 1px solid black;
}

.container {
    width: 800px;
    height: 900px;
    border: 2px solid black;
    margin: 10px auto;
    box-shadow: 6px 6px 20px darkslategrey;
    background-image: url("./courses/pexels-photo-688016.jpeg");
    background-size: cover;
    background-position: center;
    /* this is to have grid */
    display: grid;
    grid-template-columns: repeat(4, 25%);
    grid-template-rows: repeat(6, 1fr);
    grid-template-areas:
        "door3 door13 door7 door21"
        "door22 door6 door17 door11"
        "door12 door23 door16 door24"
        "door9 door20 door8 door19"
        "door15 door1 door14 door4"
        "door2 door5 door18 door10";

}

.image {
    background-image: none;
    background-size: cover;
    background-position: center;
    /*grid-area: door5;*/
}

.text {
    font-weight: 900;
    font-size: 20px;
    height: 100%;
    width: 100%;
    color: greenyellow;
    padding: 10px;
    border: 1px dashed greenyellow;
    /**/
    transition: opacity .6s;
}