style.css

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

:root {
    --bg-main-color: white;
    --bg-color: #cccccc;
    --text-color: black;
    --link-color: #4e4e4e;
}

ul {
    list-style: none;
}

body {
    font-family: sans-serif;
    background-color: var(--bg-color);
}

main {
    background-color: var(--bg-main-color);
    padding: 20px;
    border-radius: 15px;
    box-shadow: 3px 3px 20px 0 #030303;
    width: min(85vw, 900px);
    margin-inline: auto;
    margin-block: 50px;
}

main h1 {
    text-align: center;
    margin-block: 20px 30px;
}

main .tip {
    font-size: 20px;
    text-align: center;
    animation: tip ease-in 2s infinite;
}

@keyframes tip {
    0% {
        transform: scale(120%);
    }

    50% {
        transform: scale(100%);
    }

    100% {
        transform: scale(120%);
    }
}

main #challenges-number {
    font-size: 22px;
    margin-block: 30px;
}

main #challenges {
    display: flex;
    flex-wrap: wrap;
    gap: 40px 20px;
}

main #challenges .challenge {
    flex-grow: 1;
    flex-basis: 300px;
    overflow: hidden;
    border-radius: 15px;
}

main #challenges .challenge a:hover img {
    transform: scale(120%);
}

main #challenges .challenge a img {
    width: 100%;
    transition: transform .5s;
}

footer {
    background-color: white;
    box-shadow: 3px 3px 20px 0 #030303;
    width: min(85vw, 900px);
    margin-inline: auto;
    border-radius: 15px 15px 0 0;
    padding: 20px 20px 70px 20px;
    text-align: center;
}

footer h2 {
    margin-block: 20px;
    font-size: 28px;
}

footer p {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 50px;
}

footer ul {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
    gap: 30px 10px;
}

footer ul li a {
    font-size: 18px;
    text-decoration: none;
    color: var(--link-color);
    font-weight: 700;
}

footer ul li a:hover {
    color: var(--text-color);
    text-decoration: underline 1.5px;
}