styles.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    color: #ffffff;
    text-shadow: 0 0 2px black, 0 0 4px black;
}

body {    
    height: 100lvh;
    background-color: #3300aa;    
    transition: all .3s   
} 

.flex-center {
    display: flex;
    justify-content: center;
    align-items: center;
}

#contenedor {
    width: 50%;
    min-width: 300px;
    max-width: 500px;
    height: 40%;
    max-height: 400px;    
    background-color: #0003;
    border: 5px solid black;
    box-shadow: 0px 0px 8px 4px #0008;
    border-radius: 15px;
    flex-wrap: wrap;    
    flex-direction: column;
    justify-content: space-around;
}

#colorNum {
    font-size: 4rem;
    font-weight: bold;
}

#boton-color {
    padding: 10px 35px;
    font-size: 1.5rem;
    border-radius: 10px;
    background: #0009;
    cursor: pointer;
    user-select: none;
    transition: .4s;
    text-transform: uppercase;
}
    & #boton-color:hover {        
        background: #000c;
        text-shadow: 0 0 2px white, 0 0 4px white, 0 0 6px white;
    }

#me-gusta {
    color: white;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    background: #3300AA;
    font-size: 1.3rem;
    font-style: italic;
    text-shadow: 0 0 10px black;
    padding: 3px 20px 7px 20px;
    /* border: none; */
    transition: all .4s;
    border-radius: 10px;
    position: relative;    
}
    & #me-gusta:hover {
        text-shadow: 0 0 2px white, 0 0 4px white;
        background: #fff5 !important;
    }
span.red {    
    position: relative;
    right: -5px;
    top: 2px;
    color: red;
    font-style: normal;
    font-weight: bold;
    font-size: 1.5rem;    
}

.favoritos {
    display: inline-block;
    border-radius: 10px;
    margin: 10px;
    padding: 10px;
    border: 2px solid black;
    box-shadow: 0 0 4px 1px black;
    transition: all 0.4s;
    cursor: pointer;
    }

.nav-bar {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    max-height: 27vh;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    overflow-y: scroll;
    background-color: #30404f;
    box-shadow:inset 0px 0px 6px 2px black
}

#seleccionar {
    padding: 7px 15px;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: bold;    
}