style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-color: #05c46b;
    font-family: Verdana;
    text-align: center;
}
h4{
    margin: 15px 0 0;
}
#disp{
    font-size: 12px;
    color: red;
}
#displ{
    font-size: 12px;
    color: red;
}
#count{
    font-size: 12px;
    color: red;
}
form {
    background-color: #fff;
    font-family: Verdana;
    max-width: 500px;
    margin: 20px auto;
    padding: 30px 20px;
    box-shadow: 2px 5px 10px rgba(0, 0, 0.5);
}

.form-control {
    text-align: left;
    margin-bottom: 15px;
}
.form-control label {
    display: block;
    margin-bottom: 10px;

}

.form-control input,
.form-control select,
.form-control textarea {
    border: 1px solid #777;
    border-radius: 2px;
    font-family: inherit;
    padding: 7px;
    display: block;
    width: 90%;
}
.form-control input:focus{
    outline: none;
}

.form-control input[type="radio"],
.form-control input[type="checkbox"] {
    display: inline-block;
    width: auto;
    margin: 5px 5px;
}

#submit {
    background-color: #05c46b;
    border: 1px solid #777;
    border-radius: 5px;
    font-family: inherit;
    font-size: 21px;
    display: block;
    width: 100%;
    margin-top: 20px;
    margin-bottom: 20px;
    padding: 9px 0;
}

#reset {
    background-color: #777;
    font-family: inherit;
    font-size: 20px;
    display: block;
    width: 30%;
    padding: 8px 0;
    color: #fff;
    border: none;
    border-radius: 5px;
}

.button-reset {
    text-align: center;
    display: flex;
    justify-content: center;
}
small{
    font-size: 12px;
    color: red;
    margin: 0 5px;
    display: none;
}
.form-control.success input{
    border: 3px solid green;
    padding: 7px;
    display: block;
    width: 90%;
    text-align: left;

}
.form-control.error input{
    border: 2px solid red;
    padding: 7px;
    display: block;
    width: 90%;
    text-align: left;

}
.form-control.error small {
    display: block;
}
.form-control.success select{
    border: 3px solid green;
    padding: 7px;
    display: block;
    width: 90%;
    text-align: left;

}
.form-control.error select{
    border: 2px solid red;
    padding: 7px;
    display: block;
    width: 90%;
    text-align: left;

}
.form-control.success textarea{
    border: 3px solid green;
    padding: 7px;
    display: block;
    width: 90%;
    text-align: left;

}
.form-control.error textarea{
    border: 2px solid red;
    padding: 7px;
    display: block;
    width: 90%;
    text-align: left;

}
.form-control-c input{
    border: 2px solid green;
}
/* ` */