styles.css

* {
    box-sizing: border-box;
}

body {
    background: rgb(177, 188, 230);
    background: linear-gradient(
        180deg,
        rgba(177, 188, 230, 1) 0%,
        rgba(154, 134, 164, 1) 100%
    );
    height: 100vh;
    padding-top: 150px;
    overflow: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

.tabs {
    position: relative;
    display: flex;
}

input[type="radio"] {
    display: none;
}

.btn {
    width: min(32vw, 150px);
    height: 35px;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    top: 1px;
    left: 0;
    z-index: 2;
    cursor: pointer;
}

.tabs__content {
    visibility: hidden;
    background-color: #e2e6fd;
    border: 1px solid rgb(111, 111, 111);
    border-radius: 0 3px 3px 3px;
    padding: 1rem;
    position: absolute;
    bottom: 0;
    left: 0;
    transform: translateY(100%);
    z-index: 1;
}

#first-topic-id:checked ~ .tabs__content-first,
#second-topic-id:checked ~ .tabs__content-second,
#third-topic-id:checked ~ .tabs__content-third {
    visibility: visible;
}

#first-topic-id:checked ~ .btn-1,
#second-topic-id:checked ~ .btn-2,
#third-topic-id:checked ~ .btn-3 {
    background-color: #e2e6fd;
    border: 1px solid rgb(111, 111, 111);
    border-bottom: none;
    border-radius: 3px 3px 0 0;
}