style.css

*{
    box-sizing: border-box;
    padding: 0;
    margin: 0;
}
body{
    font-family: Poppins;
    font-size: 18px;
}
.container{
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-image: url("./assets/bg1.jpg");
    background-size: cover;
}
.area{
    width: 375px;
    height: 756px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-direction: column;
    background-color: #ffffff1f;
    border-radius: 50px;
    backdrop-filter: blur(15px);
    transition: 0.2s;
    padding: 20px 0;
    box-shadow: rgba(0, 0, 0, 0.329) 0px 22px 70px 4px;
    border: 0.5px outset #ffffff;
}
.area:hover{
    box-shadow: 0px 0px 52px 19px rgba(0, 0, 0, 0.021);
}
.popup{
    background-color: #ff0000;
    width: 100px;
    border-radius: 50px;
    padding: 5px 20px;
    margin-top: 15px;
    position: absolute;
    top: 0;
}
.operation{
    color: #adadad;
}
.input{
    padding-top: 200px;
    display: flex;
    justify-content: start;
    align-items: end;
    flex-direction: column;
    margin: 0 34px;
}
.input input{
    height: 72px;
    border: none;
    background-color: transparent;
    font-size: 26px;
    font-weight: 500;
    text-align: right;
    color: #fff;
}
.input input:focus{
    outline: none;
}
.input span{
    width: 20px;
    height: 20px;
}
.operations-content{
    width: 100%;
}
.row{
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 20px 0;
}
.row > span{
    background-color: #505050;
    color: #fff;
    width: 62px;
    height: 62px;
    margin: 0 10px;
    border-radius: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 26px;
    font-weight: 800;
    cursor: pointer;
    transition: 0.15s;
}
.row > span:hover{
    background-color: #5050508f;
}
.row:first-child > span{
    background-color: #f1f1f1;
    color: #000;
}
.row > span:nth-child(4){
    background-color: #FF9500;
    color: #fff;
}
.row:last-child > span:first-child{
    width: 144px;
}
#clock{
    display: flex;
    justify-content: center;
    align-items: center;
    color: #fff;
}