html {
    box-sizing: border-box;
}

*,
*::before,
*::after {
    box-sizing: inherit;
}

* {
    margin: 0;
    padding: 0;
}

body {
    font-family: Arial, Helvetica, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100dvh;
    padding: 12px;
    background-color: #B9CFD4;
}

.main {
    max-width:320px;
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    border: 2px solid rgba(0, 0, 0, 0.377);
    box-shadow: 4px 4px 8px rgba(43, 41, 41, 0.1);
    padding: 12px;
    border-radius: 22px;
    background-color: rgba(255, 255, 255, 0.63);
}

.display {
    width: 100%;
    height: 110px;
    border-radius: 22px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    padding: 12px;
    box-shadow: 2px 2px 4px rgba(0, 0, 0, 0.1);
    color: #ffffff;
    background-color: #1D2D44;
}

.display .result {
    font-size: 22px;
    font-weight: bold;
}

.special-buttons {
    width: 100%;
    display: flex;
    margin-top: 12px;
    justify-content: center;
}

.special-column {
    flex: 1;
    display: flex;
    justify-content: center;
}

.special-buttons button{
    width: 60px;
    height: 60px;
    border-radius: 50%;
    border: none;
    background-color: #F40000;
    color: #ffffff;
    font-weight: bold;
    cursor: pointer;
    font-size: 20px;
    transition: 0.1s ease-in-out;
    display: flex;
    align-items: center;
    justify-content: center;
}

.special-buttons button:hover {
    opacity: 0.8;
}

.backspace span {
    font-size: 28px;
}

.columns {
    width: 100%;
    display: flex;
    margin-top: 8px;
}

.column1,
.column2,
.column3,
.column4 {
    display: flex;
    flex-direction: column;
    flex: 1;
    align-items: center;
    row-gap: 8px;
}

.column button {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    border: none;
    cursor: pointer;
    color: #ffffff;
    font-weight: bold;
    font-size: 20px;
    transition: 0.1s ease-in-out;
}

.column button:hover {
    opacity: 0.8;
}

.column1 button,
.column2 button,
.column3 button {
    background-color: #1D2D44;
}

.column3 button:last-child {
    background-color: #FF8600;
}

.column4 button {
    background-color: #256EFF;
}