* {
    box-sizing: border-box;
}

:root {
    --page-bg: #f0f0f0;
    --page-pattern: rgba(156, 146, 172, 0.05);
    --page-text: #333333;
    --heading-shadow: rgba(0, 0, 0, 0.1);
    --toggle-bg: #ffffff;
    --toggle-text: #202124;
    --toggle-border: rgba(0, 0, 0, 0.12);
    --toggle-shadow: rgba(0, 0, 0, 0.12);
    --card-bg: #ffffff;
    --card-text: #333333;
    --card-shadow-primary: rgba(0, 0, 0, 0.1);
    --card-shadow-secondary: rgba(0, 0, 0, 0.05);
    --button-bg: #4CAF50;
    --button-text: #ffffff;
    --button-shadow: rgba(76, 175, 80, 0.4);
    --button-shadow-hover: rgba(76, 175, 80, 0.6);
}

:root[data-theme="dark"] {
    --page-bg: #121417;
    --page-pattern: rgba(255, 255, 255, 0.06);
    --page-text: #f4f6f8;
    --heading-shadow: rgba(0, 0, 0, 0.45);
    --toggle-bg: #20242a;
    --toggle-text: #f4f6f8;
    --toggle-border: rgba(255, 255, 255, 0.18);
    --toggle-shadow: rgba(0, 0, 0, 0.35);
    --card-bg: #1c2026;
    --card-text: #f4f6f8;
    --card-shadow-primary: rgba(0, 0, 0, 0.45);
    --card-shadow-secondary: rgba(0, 0, 0, 0.28);
    --button-bg: #2f9e63;
    --button-text: #ffffff;
    --button-shadow: rgba(47, 158, 99, 0.34);
    --button-shadow-hover: rgba(47, 158, 99, 0.5);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    margin: 0;
    min-height: 100vh;
    background-color: var(--page-bg);
    background-image:
        linear-gradient(45deg, transparent 45%, var(--page-pattern) 45%, var(--page-pattern) 55%, transparent 55%),
        linear-gradient(-45deg, transparent 45%, var(--page-pattern) 45%, var(--page-pattern) 55%, transparent 55%);
    background-size: 60px 60px;
    color: var(--page-text);
    text-align: center;
    transition: background-color 0.25s ease, color 0.25s ease;
}

.app-shell {
    position: relative;
    display: grid;
    place-items: center;
    align-content: center;
    min-height: 100vh;
    padding: 72px 24px 40px;
}

.theme-toggle {
    position: absolute;
    top: 24px;
    right: 24px;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    min-width: 104px;
    min-height: 44px;
    padding: 10px 16px;
    border: 1px solid var(--toggle-border);
    border-radius: 999px;
    background: var(--toggle-bg);
    color: var(--toggle-text);
    box-shadow: 0 8px 24px var(--toggle-shadow);
    cursor: pointer;
    font: inherit;
    font-weight: 700;
    justify-content: center;
    transition: transform 0.2s ease, background-color 0.25s ease, color 0.25s ease, border-color 0.25s ease;
}

.theme-toggle:hover {
    transform: translateY(-2px);
}

.theme-toggle__icon {
    font-size: 1.1rem;
    line-height: 1;
}

h1 {
    font-size: 3rem;
    font-weight: 800;
    color: var(--page-text);
    text-shadow: 0 4px 8px var(--heading-shadow);
}

@media (max-width: 560px) {
    .app-shell {
        padding: 88px 16px 32px;
    }

    .theme-toggle {
        top: 16px;
        right: 16px;
    }

    h1 {
        font-size: 2.25rem;
    }
}