style.css

:root {
    /* Color for Light Mode */
    --bg-color:#F1EAFF;
    --bg-text-color: #000;
    --text-color: #000;
    --keypad-bg-color: #F1EAFF;
    --keypad-bg-color2: #fff;

    /* color for Dark Mode */
    --bg-color:#040D12;
    --bg-text-color: #fff;
    --text-color: #fff;
    --keypad-bg-color: #040D12;
    --keypad-bg-color2: #183D3D;
    
}
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
.heading {
    height: 5vh;
    font-size: 1em;
    font-weight: 700;
    color: var(--text-color);
}
body {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: var(--bg-color);
    flex-direction: column;
}
.calculator {
    height: 550px;
    max-width: 350px;
    padding: 20px;
    background-color: var(--keypad-bg-color);
    border-radius: 10px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    border: 5px solid black;
}

/* display result section */
.display {
    height: 20%;
    border-radius: 5px;
    border: 2px solid black;
    background-color: var(--bg-color);
}
.display input {
    height: 100%;
    width: 100%;
    background-color: transparent;
    border: none;
    outline: none;
    text-align: right;
    font-size: 2em;
    color: var(--text-color);
}

/* Theme Switch Section */
.theme-switch {
    display: flex;
    align-items: center;
    justify-content: flex-end;
    margin-bottom: 10px;
}
.theme-toggle-label {
    height: 20px;
    width: 40px;
    display: inline-block;
    background-color: var(--keypad-bg-color2);
    border:2px solid black;
    border-radius: 20px;
    position: relative;
    cursor: pointer;
}
.theme-toggle-label:after {
    content: "";
    position: absolute;
    width: 16px;
    height: 16px;
    background-color: #fff;
    border-radius: 50%;
    transition: 0.3s ease;
}
.theme-switch input {
    display: none;
}
.theme-switch input:checked+.theme-toggle-label::after {
    transform: translateX(20px);
}

/* Button Section */
.keys {
    display: grid;
    grid-template-columns: repeat(4,1fr);
    gap: 20px;
    height: 70%;
}
.keys button{
    border-radius: 5px;
    padding: 5px;
    font-size: 2em;
    cursor: pointer;
    outline: none;
    background-color: var(--bg-color);
    color: var(--text-color);
}
button:hover {
    background-color: green;
    color: white;
    transition: 1s;
}
.keys button.equal{
    background-color: orange;
}
.keys button.equal:hover {
    background-color: green;
    color: white;
    transition: 1s;
}