style.css

body {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 20px;
    padding: 0 20px 30px 0;
    line-height: 1.4;
}
.flex-container{
    margin-top: 10px;
    display: flex;
    flex-wrap: nowrap;
    width: 100%;
    height: 200px;
    justify-content: center;
    transition: 2s all ease;
}

.flex-item{
    background: rgb(45,41,38);
    border: 1pt solid rgb(233,75,60);
    width: 10px;
    transition: 0.1s all ease;
}

.row{
    display: grid;
    grid-template-columns: 1fr 1fr 2fr;
}

#input{
    display: flex;
    padding: 10px;
    justify-content: space-around;
}

.button{
        font-size: 7px;
        margin: 3px 1px;
        transition-duration: 0.4s;
        cursor: pointer;
        opacity: 1;
        font-family: roboto;
        padding: 10px 40px;
        border: 1px solid rgb(233,75,60);
        border-radius: 50px;
        text-transform: uppercase;
        letter-spacing: 2px;
        font-weight: bold;
        color: rgb(233,75,60);
        text-align: center;
        
        
      }

      .n{
        font-size: 7px;
        margin: 3px 1px;
        transition-duration: 0.4s;
        cursor: pointer;
        opacity: 1;
        font-family: roboto;
        padding: 10px 42px;
        border: 1px solid rgb(233,75,60);
        border-radius: 50px;
        text-transform: uppercase;
        letter-spacing: 2px;
        font-weight: bold;
        color: silver;
        text-align: center;
      }

      .b1 {
        background-color: rgb(45,41,38); 
        color:rgb(233,75,60); 
        border: 2px solid rgb(233,75,60);
      }
      
      .b1:hover {
        background-color: rgb(233,75,60);
        color: rgb(45,41,38);
      
      }

      .b2 {
        background-color: rgb(45,41,38); 
        color:silver; 
        border: 2px solid silver;
      }
      
      .b2:hover {
        background-color: silver;
        color: rgb(45,41,38);
      
      }
      .slidecontainer {
        width: 100%;
      }
      
      .slider {
        -webkit-appearance: none;
        width: 100%;
        height: 15px;
        border-radius: 5px;
        background: #d3d3d3;
        outline: none;
        opacity: 0.7;
        -webkit-transition: .2s;
        transition: opacity .2s;
      }
      
      .slider:hover {
        opacity: 1;
      }
      
      .slider::-webkit-slider-thumb {
        -webkit-appearance: none;
        appearance: none;
        width: 25px;
        height: 25px;
        border-radius: 50%;
        background: rgb(45,41,38);
        border: 2px solid rgb(233,75,60);
        cursor: pointer;
      }
      
      .slider::-moz-range-thumb {
        width: 25px;
        height: 25px;
        border-radius: 50%;
        background: #04AA6D;
        cursor: pointer;
      }