* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    outline: none;
    font-family: "Noto Sans", sans-serif;
}

html {
    font-size: 62.5%;
}

.container {
    width: 100%;
    height: 100vh;
    background-color: #1e2224;
    display: flex;
    justify-content: center;
    align-items: center;
}

.calculator {
    width: 40rem;
    height: 60rem;
    background-color: #2e2f30;
    padding: 3rem 2rem;
    border-radius: 2rem;
    box-shadow: 0 1rem 3rem rgba(0, 0, 0, 0.4);
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
}

.screen {
    width: 34rem;
    height: 8rem;
    background-color: #8d8d8d;
    margin-bottom: 1.5rem;
    border-radius: 1rem;
    border: none;
    pointer-events: none;
    text-align: right;
    font-size: 2rem;
    letter-spacing: 0.1rem;
    color: #fff;
    padding: 2rem;
}

.btn, .equal {
    width: 7rem;
    height: 7rem;
    margin: 1rem;
    border: none;
    background: linear-gradient(180deg, #2f2f2f, #3f3f3f);
    box-shadow: inset 0 -0.8rem 0.8rem rgba(0, 0, 0, 0.25), 
    0 0 0 0.2rem rgba(0, 0, 0, 0.75), 1rem 2rem 2.5rem rgba(0, 0, 0, 0.4);
    border-radius: 1rem;
    cursor: pointer;
    position: relative;
}

.clear {
    width: 25rem;
    background: #d62929;
}

.btn::before,
.equal::before {
    content: attr(data-num);
    position: absolute;
    top: 0.3rem;
    left: 0.4rem;
    bottom: 0.7rem;
    right: 1.2rem;
    display: flex;
    justify-content: center;
    align-items: center;
    color: #fff;
    font-size: 2.2rem;
    background: linear-gradient(90deg, #2d2d2d, #4d4d4d);
    box-shadow: -0.5rem -0.5rem 1.5rem rgba(0, 0, 0, 0.1), 
    1rem 0.5rem 1rem rgba(0, 0, 0, 0.15);
    border-left: 0.1rem solid #0004;
    border-bottom: 0.1rem solid #0004;
    border-top: 0.1rem solid #0004;
    border-radius: 1rem;
}

.clear::before {
    background: #d62929;
    border-left: 0.1rem solid #fff4;
    border-bottom: 0.1rem solid #fff4;
    border-top: 0.1rem solid #fff4;
}

.equal {
    background: #37925a;
}

.equal::before {
    background: #37925a;
    border-left: 0.1rem solid #fff4;
    border-bottom: 0.1rem solid #fff4;
    border-top: 0.1rem solid #fff4;
}

.btn:active,
.equal:active {
    filter: brightness(1.5);
}