style.css

* {
    margin: 0;
    padding: 0;
}

.game-heading {
    text-align: center;
    font-family: Arial, Helvetica, sans-serif;
    color: red;
    text-shadow: 3px 2px green;
    font-size: 5em;
    margin: 40px 0;
}

.game {
    width: 800px;
    height: 300px;
    margin: 60px auto;
    display: flex;
    border: 3px solid red;
}

.cactus {
    height: 40px;
    object-fit: contain;
    position: relative;
    top: 261px;
    left: 670px;
    animation: block 3s infinite linear;
}

.block {
    height: 40px;
}

.character {
    height: 100px;
}

.dino {
    height: 100px;
    object-fit: contain;
    position: relative;
    top: 203px;
}

.animate {
    animation: character 500ms;
}

@keyframes block {
    0% {
        left: 670px;
    }
    100% {
        left: -60px;
    }
}

@keyframes character {
    0% {
        top: 203px;
    }
    30% {
        top: 140px;
    }
    70% {
        top: 140px;
    }
    100% {
        top: 203px;
    }
}