style.css

@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;500;600;700;800&display=swap');

*{
    margin: 0;
    padding: 0;
    border: none;
    outline: none;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}

body{
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: 0 10px;
    background: #221f2f;
    overflow: hidden;
}

body::before{
    content: "";
    position: absolute;
    width: 120px;
    height: 120px;
    background-color: #ed2ff0;
    left: 15%;
    top: 20%;
    filter: blur(150px);
}

body::after{
    content: "";
    position: absolute;
    width: 120px;
    height: 120px;
    background-color: #22a8cd;
    left: 80%;
    top: 74%;
    filter: blur(150px);
}

.container {
    width: 25rem;
    color: #fff;
    background: rgba(0, 0, 0, 0.44);
    padding: 20px 30px;
    border-radius: 16px;
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(7.4px);
    -webkit-backdrop-filter: blur(7.4px);
    border: 1px solid rgba(0, 0, 0, 0.1);
}

.container h2{
    font-size: 1.6rem;
    font-weight: 500;
    text-align: center;
}

.container form{
    margin: 30px 0 10px 0;
}

.container form p{
    font-size: 1rem;
    margin-bottom: 7px;
}

.container form input{
    height: 40px;
    width: 100%;
    border-radius: 5px;
    font-size: 1rem;
    padding: 0 15px;
    background: transparent;
    color: #fff;
    border: 1px solid #999;
    transition: all 0.3s ease;
}

.container form input:hover{
    border: 1px solid #675afe;
}

.container form input:focus{
    padding: 0 14px;
    border: 1px solid #675afe;
}

.container form .convert-box{
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: space-between;
    margin-top: 20px;
}

.container form .from, .container form .to{
    width: 100%;
}

.container .convert-box .select-input{
    display: flex;
    width: 100%;
    border: 1px solid #999;
    height: 40px;
    align-items: center;
    border-radius: 5px;
    padding: 0 20px;
    background: transparent;
    cursor: pointer;
    transition: all 0.3s ease;
}

.container .convert-box .select-input:hover{
    border: 1px solid #675afe;
}

.container .convert-box .select-input img{
    max-width: 20px;
}

.container .convert-box .select-input select{
    width: 100%;
    cursor: pointer;
    font-size: 1rem;
    background: none;
    margin: 0 -5px 0 5px;
    color: #fff;
}

.container .convert-box .select-input select option{
    color: #000;
}

.container .convert-box .reverse{
    cursor: pointer;
    margin-top: 32px;
    font-size: 22px;
    transform: rotate(90deg);
    transition: all 0.3s ease;
}

.container .convert-box .reverse:hover{
    color: #675afe;
}

.container form .result{
    font-size: 1.1rem;
    margin: 20px 0 30px;
}

.container form button{
    width: 100%;
    height: 42px;
    color: #fff;
    background: #20232c;
    font-size: 1rem;
    cursor: pointer;
    border-radius: 5px;
    transition: all 0.3s ease;
}

.container form button:hover{
    background: #675afe;
}