body{
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 16px;
    background-color: hsl(0, 0%, 95%);
}

* {
    box-sizing: border-box;
}

#calculator{
    background-color: hsl(0, 0%, 15%);
    font-family: Arial, Helvetica, sans-serif;
    border-radius: 15px;
    width: min(500px, 100%);
    overflow: hidden;
}

#display-row{
    display: flex;
    gap: 12px;
    padding: 20px 20px 0;
    align-items: stretch;
}

#display{
    flex: 1;
    min-width: 0;
    min-height: 84px;
    padding: 20px;
    border: none;
    background-color: hsl(0, 0%, 20%);
    text-align: left;
    color: white;
    font-size: clamp(1.5rem, 6vw, 2.75rem);

}

#keys{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 20px;

}

button{
    width: 100%;
    aspect-ratio: 1 / 1;
    border-radius: 50%;
    border: none;
    background-color: hsl(0, 0%, 30%);
    color: white;
    font-size: clamp(1.5rem, 6vw, 3rem);
    font-weight: bold;
    cursor: pointer;
}

button:hover{
      background-color: hsl(0, 0%, 40%);
}
button:active{
      background-color: hsl(0, 0%, 50%);
}

.operator-btn{
      background-color: hsl(40, 100%, 55%);
}

.backspace-btn{
    width: auto;
    flex: 0 0 64px;
    aspect-ratio: auto;
    border-radius: 15px;
    font-size: clamp(1.1rem, 3.8vw, 1.6rem);
    padding: 0;
    background-color: hsl(0, 0%, 30%);
}

.backspace-btn:hover{
    background-color: hsl(0, 0%, 40%);
}

.backspace-btn:active{
    background-color: hsl(0, 0%, 50%);
}

.operator-btn:hover{
    background-color: hsl(40, 100%, 65%);
}
.operator-btn:active{
    background-color: hsl(40, 100%, 75%);
}

@media (max-width: 520px){
    body{
        align-items: flex-start;
        padding: 12px;
    }

    #calculator{
        border-radius: 12px;
    }

    #display-row{
        gap: 8px;
        padding: 12px 12px 0;
    }

    #display{
        min-height: 64px;
        padding: 14px;
    }

    #keys{
        gap: 8px;
        padding: 12px;
    }

    .backspace-btn{
        flex-basis: 52px;
        border-radius: 12px;
    }
}

@media (max-width: 340px){
    #display-row{
        gap: 6px;
    }

    #display{
        padding: 12px;
    }

    #keys{
        gap: 6px;
    }

    .backspace-btn{
        flex-basis: 46px;
    }
}