body {
    display: grid;
    padding: 20px;
    background: #bebebe;
}
.phase {
    display: none;
    outline: 1px solid black;
    padding: 10px;
    background: #676767;
}
.day {
    display: none;
    outline: 1px solid #00ad14;
    padding: 10px;
    background: #000000;
}
.workout {
    grid-column-start: 1;
    grid-column-end: 2;
    padding: 10px;
    outline: 1px solid #00ad14;
    background: white;
}
.sets {
    grid-column-start: 2;
    grid-column-end: 3;
    padding: 10px;
    outline: 1px solid #00ad14;
    background: white;
}
.collapsible {
    margin-top: 15px;
     background-color: #ffffff;
     color: #000000;
     cursor: pointer;
     padding: 10px;
     width: 100%;
     border: none;
     text-align: center;
     outline: 1px solid black;
     font-size: 15px;
 }
.active, .collapsible:hover {
    background-color: #000000;
    color: #00ad14;
}
.back-btn {
    position: static;
    margin: 10px auto 15px 10px;
    padding: 10px 15px;
    border: 1px solid black;
    border-radius: 10px;
    background: black;
    color: white;
}
.back-btn:hover {
    cursor: pointer;
    background: white;
    color: black;
}