di-stepper/assets/css/stepper.css

:root {
    --primary: hsl(82.3, 54.4%, 44.7%);
    --secondary: hsl(194.5, 100.0%, 26.9%);
    --gray: hsl(37.5, 25.0%, 93.7%);
    --container: hsl(37.5, 50.0%, 96.9%);
}

.stepper {

    .fancy-checkbox {
        display: flex;
        align-items: center;
        input {
            flex: 0 0 auto;
            width: auto;
        }
        span {
            flex: 1 0 auto;
        }
    }

    .slider {
        display: flex;
        flex-wrap: nowrap;
        scroll-snap-type: x proximity;
        scroll-behavior: smooth;
        overflow-x: hidden;

        & > * {
            flex: 0 0 100%;
            scroll-snap-align: start;
        }
    }

    .button-row {
        display: grid;
        grid-template-columns: max-content 1fr;
        grid-gap: 0.5rem;
    }

    form {
        font-family: sans-serif;
        & > div {
            h2 {
                color: var(--secondary);
                text-align: center;
            }

            .radio-grid {
                display: grid;
                grid-gap: 2rem;
                grid-template-columns: repeat(3, 1fr);
                margin-top: 1rem;

                label {
                    height: 20rem;
                    @media screen and (max-width: 1024px) {
                        height: 15rem;
                    }
                    @media screen and (max-width: 980px) {
                        height: 14rem;
                    }
                    @media screen and (max-width: 768px) {
                        height: 15rem;
                    }
                    @media screen and (max-width: 580px) {
                        height: 14rem;
                    }
                    position: relative;

                    input {
                        visibility: hidden;
                        z-index: -99;
                        position: absolute;
                    }
                    input + span {
                        border: 1px var(--primary) solid;
                        border-radius: 2rem;
                        overflow: hidden;
                        cursor: pointer;
                        background: white;
                        display: flex;
                        flex-direction: column;
                        align-items: center;
                        position: absolute;
                        top: 0;
                        left: 0;
                        width: 100%;
                        height: 100%;

                        span:first-child {
                            display: flex;
                            flex: 1 0 0;
                            justify-content: center;
                            align-items: center;
                        }

                        span:nth-child(2) {
                            flex: 0 0 4rem;
                            background: var(--gray);
                            display: flex;
                            width: 100%;
                            justify-content: center;
                            align-items: center;
                        }
                    }
                    input:checked + span {
                        border-color: var(--secondary);
                    }

                    svg {
                        color: var(--secondary);
                        fill: currentColor;
                        width: 5.625rem;
                        height: 5.625rem;
                        @media screen and (max-width: 580px) {
                            width: 4rem;
                            height: 4rem;
                            &.icon-immobilienfinanzierung {
                                width: 5rem;
                                height: 5rem;
                            }
                        }
                    }
                    svg.icon-immobilienfinanzierung {
                        width: 9.6875rem;
                        height: 9.6875rem;
                    }
                }
            }

            .form-container {
                background: var(--container);
                border-radius: 2rem;
                padding: 3rem;
                display: grid;
                grid-gap: 1rem;

                .separator {
                    background: white;
                    height: 5px;
                }

                .form-grid {
                    display: grid;
                    grid-gap: 0.5rem;
                    grid-template-columns: 2fr 3fr 30px;
                    align-items: center;

                    input[type="text"], input[type="number"], input[type="tel"] {
                        font-weight: bold;
                        border: var(--primary) 1px solid;
                        text-align: right;
                    }

                    input::-webkit-outer-spin-button,
                    input::-webkit-inner-spin-button {
                        -webkit-appearance: none;
                        margin: 0;
                    }

                    .unit {
                        text-align: right;
                    }

                    .comment {
                        grid-column: 1 / -1;
                        font-size: 1.5rem;
                    }
                }
            }
        }
    }

    .step {
        height: 5px;
        position: relative;

        div {
            position: absolute;
            transition: width 0.5s;
            top: 0;
            left: 0;
            height: 100%;
            background: var(--primary);
        }
    }
}