:root {
    --color-background: #f8f9fb;
    --color-on-background: #202124;
    --color-surface: #ffffff;
    --color-surface-hover: #f0f1f5;
    --color-primary: #0078ff;
    --color-primary-hover: #005fcc;
    --color-on-primary: #ffffff;
    --color-error: #e53935;
    --color-on-error: #ffffff;
    --radius: 0.75rem;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    --transition: 0.2s ease;
}

main.dark,
header.dark {
    color-scheme: dark;
    --color-background: #121212;
    --color-on-background: #e5e5e5;
    --color-surface: #1e1e1e;
    --color-surface-hover: #2a2a2a;
    --color-primary: #4a6cf7;
    --color-primary-hover: #3b5be6;
    --color-on-primary: #ffffff;
    --color-error: #ff4d4f;
    --color-on-error: #ffffff;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

html,
body {
    height: 100%;
    margin: 0;
    font-family: 'Inter', 'Segoe UI', Roboto, sans-serif;
    background: var(--color-background);
    color: var(--color-on-background);
}

body {
    display: flex;
    flex-direction: column;
    transition: background var(--transition), color var(--transition);
}

/* Header */
header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 2rem;
    height: 4rem;
    background-color: var(--color-primary);
    color: var(--color-on-primary);
    box-shadow: var(--shadow);
    transition: background var(--transition);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

header .logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-weight: 600;
    font-size: 1.1rem;
}

header .nav {
    display: flex;
    gap: 1.5rem;
}

header .nav a {
    color: var(--color-on-primary);
    text-decoration: none;
    font-weight: 500;
    transition: opacity var(--transition);
}

header .nav a:hover {
    opacity: 0.8;
}

/* Main layout */
main {
    flex: 1;
    display: grid;
    grid-template-columns: 1fr 2fr 1fr;
    column-gap: 2rem;
    padding: 2rem;
    background: var(--color-background);
    transition: background var(--transition);
}

main > div {
    background: var(--color-surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow-y: auto;
    padding: 1.5rem;
    transition: background var(--transition), box-shadow var(--transition);
}

main > div:hover {
    background: var(--color-surface-hover);
}

/* Spinner */
.spinner {
    display: flex;
    align-items: center;
    justify-content: center;
    grid-column: span 3;
    color: var(--color-primary);
}

/* Inputs */
input[type="checkbox"] {
    appearance: none;
    width: 1.25rem;
    height: 1.25rem;
    border: 2px solid var(--color-primary);
    border-radius: 4px;
    cursor: pointer;
    position: relative;
    transition: all var(--transition);
}

input[type="checkbox"]:checked {
    background-color: var(--color-primary);
    border-color: var(--color-primary);
}

input[type="checkbox"]:checked::after {
    content: "✔";
    color: var(--color-on-primary);
    font-size: 0.8rem;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -55%);
}