style.css

body {
    margin: 40px 0 40px 0;
    padding: 0;
    border: none;
    outline: none;
    /* background-color: #eee; */
    background-color: #e35267;
    box-shadow: none;
    font-family: 'Montserrat', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
}

main {
    background-color: white;
    padding: 10px 40px 40px 40px;
    display: block;
    text-align: left;
    max-width: 500px;
    margin: auto;
    border-radius: 10px;
}

header {
    text-align: center;
}

h1 {
    font-size: 40px;
    color: #191516;
    font-weight: bold;
}

form {
    display: flex;
    flex-direction: column;
    font-size: 22px;
}

#name, #email, #number, #dropdown {
    outline: none;
    width: 100%;
    padding: 7px;
    font-size: 16px;
    border: 1px solid #dee2e6;
    border-radius: 3px;
    background-color: white;
    box-sizing: border-box;
}

#dropdown, option {
    outline: none;
}

select {
    padding: 7px;
}

textarea {
    display: block;
}

.form-group {
    padding: 8px 0;
    margin-bottom: 2px;
}

.form-group>label {
    margin-bottom: 8px;
    color: #191516;
    display: block;
    font-weight: 500;
}

[type="checkbox"]+label>span, [type="radio"]+label {
    font-size: 16px;
}

[type="checkbox"], [type="radio"] {
    margin: 0 8px 0 0;
    box-sizing: border-box;
    min-width: 18px;
    min-height: 18px;
}

/*hide the original checkbox and radio button*/

[type="checkbox"] , [type="radio"] {
    opacity: 0;
    pointer-events: none;
}


.radio-group, .checkbox-group {
    display: flex;
    flex-direction: row;
    margin-bottom: 10px;
    position: relative;
}

[type="radio"]+label {
    margin: 0 5px 0 0;
    font-size: 16px;
    position: relative;
    cursor: pointer;
}

[type="checkbox"]+label {
    margin: 0 5px 0 0;
    font-size: 16px;
    position: relative;
    cursor: pointer;
}

/* this is the custom box for the checkbox*/

[type="checkbox"]+label::before {
    content: '';
    min-width: 18px;
    min-height: 18px;
    position: absolute;
    left: -26px;
    border-radius: 3px;
    /* top: 5px; */
    background-color: #eee;
    transition: all 0.4s;
}

/* custom checkmark made using only css*/

/* 
[type="checkbox"]+label::after {
    content: '';
    min-width: 0px;
    min-height: 0px;
    position: absolute;
    left: -20px;
    top: 2px;
    border-right: 1px solid white;
    border-bottom: 1px solid white;
    background-color:red; 
    transform: rotateZ(40deg);
    transition:  all 0.4s;

}  
*/

/* this will unhide the custom checkmark */

/* [type="checkbox"]:checked +label::after {
    min-width: 5px;
    min-height: 10px;
} */

/* this is the svg for the checkmark */

[type="checkbox"]+label svg {
    position: absolute;
    width: 28px;
    left: -31px;
    top: -5px;
}

/* this is the polyline for the checkmark svg */

[type="checkbox"]+label svg polyline {
    stroke: white;
    stroke-width: 8;
    fill: none;
    stroke-dasharray: 70;
    stroke-dashoffset: 70;
    transition: stroke-dashoffset 0.4s;
}

/* change the color of custom checkbox when the original checkbox is in checked state */

[type="checkbox"]:checked+label::before {
    background-color: #191516;
}

/* setting stroke-dashoffset to 0 will reveal the hidden checkmark */

[type="checkbox"]:checked+label svg polyline {
    stroke-dashoffset: 0;
}

textarea {
    width: 100%;
    box-sizing: border-box;
    height: 200px;
    resize: none;
    padding: 4px;
    font-size: 16px;
    border: 1px solid #dee2e6;
}

button {
    width: 100%;
    display: block;
    height: 40px;
    background-color: #191516;
    border: none;
    font-weight: bold;
    font-size: 20px;
    color: white;
    box-sizing: border-box;
}

#description {
    text-align: center;
    font-style: italic;
    margin-top: -10px;
}

/* custom circle for radio button*/
[type="radio"]+label::before {
    content: '';
    position: absolute;
    border-radius: 50%;
    background-color: #eee;
    left: -27px;
    top: -1px;
    width: 20px;
    height: 20px;
    transition: all 0.4s;
}

/* fill circle with inset shadow when it is selected*/
[type="radio"]:checked+label::before {
    box-shadow: inset 0 0 0 6px #191516;
}


@media (max-width: 540px) {
 main {
        max-width: 380px;
    }
}
@media (max-width: 460px) {
    main {
        max-width: 280px;
    }
    h1 {
        font-size: 32px;
    }
    #description {
        font-size: 15px;
    }
    form {
        font-size: 18px;
    }
    #name, #email, #number, #dropdown, textarea {
        font-size: 15px;
    }
    [type="radio"]+label, [type="checkbox"]+label>span {
        font-size: 15px;
    }
}

@media (max-width: 375px) {
 main {
        max-width: 260px;
        padding: 10px 30px 30px 40px;
    }
    h1 {
        font-size: 28px;
    }
    #description {
        font-size: 12px;
    }
    form {
        font-size: 15px;
    }
    #name, #email, #number, #dropdown, textarea {
        font-size: 12px;
    }
    [type="radio"]+label, [type="checkbox"]+label>span {
        font-size: 12px;
    }
    button {
        font-size: 18px;
    }
}

@media (max-width: 320px) {
 main {
        max-width: 220px;
    }
}

@media (max-width: 280px) {
 main {
        max-width: 180px;
    }
}