:root {
    --color-primary: #004080;
    --color-secondary: #007bff;
    --color-accent: #6c757d;
    --color-background: #f8f9fa;
    --color-surface: #ffffff;
    --color-text-primary: #212529;
    --color-text-secondary: #495057;
    --color-text-on-primary: #ffffff;
    --color-text-on-secondary: #ffffff;
    --color-error: #dc3545;
    --color-success: #28a745;
    --spacing-small: 0.5rem;
    --spacing-medium: 1rem;
    --spacing-large: 1.5rem;
    --border-radius: 0.25rem;
    --font-family-base: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    --line-height-base: 1.6;
    --transition-duration: 0.2s;
}

@media (prefers-color-scheme: dark) {
    :root {
        --color-primary: #0056b3;
        --color-secondary: #007bff;
        --color-accent: #adb5bd;
        --color-background: #343a40;
        --color-surface: #454d55;
        --color-text-primary: #e9ecef;
        --color-text-secondary: #ced4da;
        --color-text-on-primary: #ffffff;
        --color-text-on-secondary: #ffffff;
        --color-error: #f5707f;
        --color-success: #33cc5a;
    }
}

body {
    margin: 0;
    font-family: var(--font-family-base);
    line-height: var(--line-height-base);
    color: var(--color-text-primary);
    background-color: var(--color-background);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    scroll-behavior: smooth;
}

header {
    background-color: var(--color-surface);
    padding: var(--spacing-medium) var(--spacing-large);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

nav ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    gap: var(--spacing-medium);
}

nav a {
    text-decoration: none;
    color: var(--color-text-primary);
    transition: color var(--transition-duration) ease;
}

nav a:hover,
nav a:focus {
    color: var(--color-secondary);
}

nav span[data-site-name] {
    font-weight: bold;
    font-size: 1.2em;
    color: var(--color-primary);
}

main {
    flex: 1;
    padding: var(--spacing-large);
    max-width: 960px;
    margin: 0 auto;
    width: 100%;
    box-sizing: border-box;
}

main h1, main h2, main h3 {
    color: var(--color-primary);
    margin-bottom: var(--spacing-medium);
    line-height: 1.3;
}

main h1 { font-size: 2em; }
main h2 { font-size: 1.75em; }
main h3 { font-size: 1.5em; }

p {
    margin-bottom: var(--spacing-medium);
}

a {
    color: var(--color-secondary);
    text-decoration: none;
}

a:hover, a:focus {
    text-decoration: underline;
}

form {
    background-color: var(--color-surface);
    padding: var(--spacing-large);
    border-radius: var(--border-radius);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    margin-bottom: var(--spacing-medium);
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-medium);
    align-items: center;
}

form label {
    display: block;
    margin-bottom: var(--spacing-small);
    font-weight: bold;
    flex-basis: 100%;
}

form input[type="email"],
form input[type="text"],
form textarea {
    padding: var(--spacing-small) var(--spacing-medium);
    border: 1px solid #ccc;
    border-radius: var(--border-radius);
    font-size: 1rem;
    flex-grow: 1;
    min-width: 180px;
    box-sizing: border-box;
}

form textarea {
    min-height: 100px;
    resize: vertical;
}

form button {
    background-color: var(--color-secondary);
    color: var(--color-text-on-secondary);
    padding: var(--spacing-small) var(--spacing-medium);
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 1rem;
    transition: background-color var(--transition-duration) ease;
}

form button:hover,
form button:focus {
    background-color: #0056b3;
}

#subscription-message,
#unsubscribe-message {
    margin-top: var(--spacing-small);
    font-weight: bold;
}

#subscription-message.error,
#unsubscribe-message.error {
    color: var(--color-error);
}

#subscription-message.success,
#unsubscribe-message.success {
    color: var(--color-success);
}

footer {
    background-color: var(--color-text-primary);
    color: var(--color-text-on-primary);
    text-align: center;
    padding: var(--spacing-medium) var(--spacing-large);
    margin-top: var(--spacing-large);
    font-size: 0.9em;
}

footer nav ul {
    justify-content: center;
    gap: var(--spacing-large);
    margin-top: var(--spacing-small);
}

footer nav a {
    color: var(--color-text-on-primary);
}

footer nav a:hover,
footer nav a:focus {
    color: var(--color-accent);
}

.diagnostics {
    margin-top: var(--spacing-medium);
}

.diagnostics label {
    display: block;
    margin-bottom: var(--spacing-small);
    font-weight: bold;
}

.diagnostics textarea {
    width: 100%;
    background-color: var(--color-background);
    border: 1px solid #ccc;
    padding: var(--spacing-medium);
    box-sizing: border-box;
    color: var(--color-text-primary);
}

@media (max-width: 768px) {
    header nav {
        flex-direction: column;
        gap: var(--spacing-small);
        align-items: center;
    }
    header nav ul {
        flex-wrap: wrap;
        justify-content: center;
    }
    main {
        padding: var(--spacing-medium);
    }
    form {
        flex-direction: column;
        align-items: stretch;
    }
    form label {
        flex-basis: auto;
    }
    form input[type="email"],
    form button {
        flex-grow: 0;
        width: 100%;
    }
    footer {
        padding: var(--spacing-medium);
    }
    footer nav ul {
        flex-direction: column;
        gap: var(--spacing-small);
    }
}

@media (max-width: 480px) {
    :root {
        --spacing-small: 0.3rem;
        --spacing-medium: 0.7rem;
        --spacing-large: 1rem;
    }
    main h1 { font-size: 1.8em; }
    main h2 { font-size: 1.5em; }
    main h3 { font-size: 1.3em; }
}