body{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    height: 100vh;
    background-color: #f0f0f0;
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100%;
}
#calculator{
    background-color: #292929;
    border-radius: 15px;
    padding: 10px;
    max-width: 480px;
    width: 100%;
    display: flex;
    flex-direction: column;
}
#calculator #display{
    padding: 20px;
    font-size: 2rem;
    background-color: #292929;
    border: none;
    text-align: right;
    color: #fff;
    overflow: hidden;
    margin: 0 24px;
}
#display::placeholder{
    color: #fff;
}
.keys{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 20px;
}
button{
    width: 80px;
    height: 80px;
    font-size: 2rem;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    transition: transform 0.2s ease;
}
button:hover{
    transform: scale(0.9);
}
#clear-btn{
    background-color: hsl(0, 1%, 44%);
    color: rgb(255, 70, 70);
}
#clear-btn:hover{
    background-color: hsl(0, 1%, 50%);
}
#clear-btn:active{
    background-color: hsl(0, 1%, 55%);
}
.operator-btn{
    background-color: hsl(0, 1%, 44%);
    color: rgb(29, 255, 29);
}
.operator-btn:hover{
    background-color: hsl(0, 1%, 50%);
}
.operator-btn:active{
    background-color: hsl(0, 1%, 55%);
}
.number-btn{
    background-color: hsl(0, 0%, 25%);
    color: #fff;
}
.number-btn:hover{
    background-color: hsl(0, 0%, 30%);
}
.number-btn:active{
    background-color: hsl(0, 0%, 35%);
}
#backspace-btn{
    background-color: hsl(0, 1%, 44%);
    color: rgb(255, 70, 70);
}
#backspace-btn:hover{
    background-color: hsl(0, 1%, 50%);
}
#backspace-btn:active{
    background-color: hsl(0, 1%, 55%);
}
#calculate-btn{
    background-color: hsl(123, 96%, 54%);
    color: #fff;
    font-weight: bold;
}
#calculate-btn:hover{
    background-color: hsl(123, 96%, 60%);
}
#calculate-btn:active{
    background-color: hsl(123, 96%, 65%);
}

@media (max-width: 700px){
    #calculator{
        max-width: 400px;
        width: 100%;
    }
    .keys button{
        width: 60px;
        height: 60px;
        font-size: 1.5rem;
    }
    #calculator #diplay{
        font-size: 1.5rem;
    }
}
@media (max-width: 422px){
    #calculator{
        max-width: 300px;
        width: 100%;
    }
    .keys button{
        width: 50px;
        height: 50px;
        font-size: 1.3rem;
    }
    #calculator #diplay{
        font-size: 1.3rem;
    }
}