.tabela {
    margin: 0;
    display: block;
    visibility: hidden;
    overflow-y: hidden;
    height: 0px;
    transition: 500ms;
}
.periodos {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 95vw;
}
.periodo {
    width: 50%;
    height: 50px;
    font-size: 1.2rem;
    font-family: 'Montserrat', sans-serif;
    border: none;
    background: rgba(0, 0, 0, 0.1);
    cursor: pointer;
}
.periodo:nth-child(1){
    margin-top: 10px;
}
.periodo:hover {
    transition: 300ms;
    background: rgba(0, 0, 0, 0.3);

}
.active + .tabela{
    height: 310px;
    visibility: visible;
    overflow-y: auto;
}

body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}
footer {
    margin-top: auto;
}