:root {
    --color-primary: #0F3755;
    --color-white: #ffffff;
    --color-black: #000000;
    --color-lightgrey: #f0f0f0;
    --color-darkgrey: #444;
    --font-base: system-ui, sans-serif;
}

html[data-theme='dark'] {
    --color-white: #1c1c1c;
    --color-lightgrey: #2a2a2a;
    --color-black: #ffffff;
    --color-darkgrey: #ccc;
}

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

body {
    margin: 0;
    font-family: var(--font-base);
    background-color: var(--color-lightgrey);
    color: var(--color-black);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: 1rem;
}

main {
    width: 100%;
    max-width: 40rem;
    padding: 1.5rem;
    border-radius: 1rem;
    background-color: var(--color-white);
    box-shadow: 0 0.5rem 1rem rgba(0, 0, 0, 0.15);
}

header,
footer {
    text-align: center;
    margin-bottom: 1rem;
}

h1 {
    font-size: 1.75rem;
    margin: 0.5rem 0;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip: rect(0 0 0 0);
    white-space: nowrap;
    border: 0;
}

img {
    display: block;
    margin: 0 auto;
    max-width: 100%;
    height: auto;
    padding: 0 2rem;
}

footer {
    font-size: 0.875rem;
    color: var(--color-darkgrey);
}

.button-container {
    margin-top: 1.5rem;
    text-align: center;
}

#theme-toggle {
    background-color: transparent;
    border: 1px solid var(--color-darkgrey);
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    cursor: pointer;
    color: var(--color-black);
    font: inherit;
    transition: background-color 0.2s ease, color 0.2s ease;
}

#theme-toggle:hover,
#theme-toggle:focus {
    background-color: var(--color-primary);
    color: white;
    outline: none;
}