/* Base styles for the calculator */
.calculator {
    width: 300px;
    margin: 50px auto;
    font-family: Arial, sans-serif;
    border-radius: 10px;
    padding: 20px;
    transition: all 0.3s ease;
}

/* Header and theme switch */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.theme-switch {
    display: flex;
    align-items: center;
    gap: 10px;
    color: var(--text-dark);
}

.toggle {
    display: flex;
    gap: 5px;
    background: var(--toggle-bg);
    padding: 5px;
    border-radius: 20px;
}

.toggle input[type="radio"] {
    display: none;
}

.toggle input[type="radio"] + label {
    width: 15px;
    height: 15px;
    border-radius: 50%;
    background: var(--key-bg);
    cursor: pointer;
}

.toggle input[type="radio"]:checked + label {
    background: var(--key-red);
}

/* Display */
.display {
    background: var(--screen-bg);
    color: var(--text-white);
    padding: 20px;
    text-align: right;
    font-size: 2em;
    border-radius: 5px;
    margin-bottom: 20px;
}

/* Buttons */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.key {
    padding: 15px;
    font-size: 1.2em;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    background: var(--key-light);
    color: var(--text-dark);
    box-shadow: 0 3px var(--key-light-shadow);
}

.key:hover {
    opacity: 0.9;
}

.del, .reset {
    background: var(--key-bg);
    color: var(--text-white);
    box-shadow: 0 3px var(--key-shadow);
}

.equal {
    background: var(--key-red);
    color: var(--text-white);
    box-shadow: 0 3px var(--key-red-shadow);
}

.reset, .equal {
    grid-column: span 2;
}

/* Default theme (theme1) applied to root */
:root {
    --main-bg: hsl(222, 26%, 31%);
    --toggle-bg: hsl(223, 31%, 20%);
    --screen-bg: hsl(224, 36%, 15%);
    --key-bg: hsl(225, 21%, 49%);
    --key-shadow: hsl(224, 28%, 35%);
    --key-red: hsl(6, 63%, 50%);
    --key-red-shadow: hsl(6, 70%, 34%);
    --key-light: hsl(30, 25%, 89%);
    --key-light-shadow: hsl(28, 16%, 65%);
    --text-dark: hsl(221, 14%, 31%);
    --text-white: hsl(0, 0%, 100%);
}

.calculator {
    background: var(--main-bg);
}