body {
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: yellow;
    font-family: cursive;
    text-align: center;
}

.container {
    position: relative;
    width: 90vw;
    max-width: 600px;
}

.step-progress {
    position: relative;
    display: flex;
    justify-content: space-between;
}

#back-line {
    position: absolute;
    width: 100%;
    height: 5px;
    background-color: lightgray;
    border: none;
    z-index: -1;
    bottom: 15px;
}

#front-line {
    position: absolute;
    width: 0%;
    height: 5px;
    background-color: green;
    border: none;
    z-index: -1;
    bottom: 15px;
    transition: width .4s linear;
}

.step {
    position: relative;
    width: 40px;
    height: 40px;
    background-color: white;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    color: lightgray;
    font-size: 18px;
    border: 5px solid lightgray;
}

.step.checked {
    color: green;
    border-color: green;
    transition: all .4s linear;
    transition-delay: .3s;
}

.step.checked small {
    position: absolute;
    bottom: -30px;
    font-weight: 600;
    width: 50px;
    text-align: center;
}

.btn {
    background-color: slateblue;
    color: white;
    border: none;
    padding: 10px 20px;
    margin: 80px 10px 0;
    border-radius: 5px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, .3);
    cursor: pointer;
}

.btn:hover {
    opacity: 0.9;
    transition: all .3s ease;
}

.btn:active {
    transform: scale(0.96);
}

.btn:disabled {
    background-color: lightgray;
}