/* Design tokens — light + dark. */
:root {
    --c-bg: #f7f8fb;
    --c-surface: #ffffff;
    --c-surface-2: #f1f3f8;
    --c-border: #e2e6ee;
    --c-text: #0f172a;
    --c-muted: #56607a;
    --c-accent: #6366f1;
    --c-accent-hover: #4f46e5;
    --c-accent-fg: #ffffff;
    --c-success: #16a34a;
    --c-danger: #dc2626;
    --radius: 14px;
    --radius-sm: 8px;
    --shadow-sm: 0 1px 2px rgba(15,23,42,.06);
    --shadow-md: 0 6px 24px rgba(15,23,42,.08);
    --shadow-lg: 0 12px 40px rgba(15,23,42,.12);
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell,
                 "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
    --container: 1140px;
    --space-1: 4px;
    --space-2: 8px;
    --space-3: 16px;
    --space-4: 24px;
    --space-5: 32px;
    --space-6: 48px;
    --space-7: 64px;
}

@media (prefers-color-scheme: dark) {
    :root {
        --c-bg: #0b1020;
        --c-surface: #131a2e;
        --c-surface-2: #1a2340;
        --c-border: #232e51;
        --c-text: #e6e9f2;
        --c-muted: #99a3bd;
        --c-accent: #818cf8;
        --c-accent-hover: #a5b4fc;
        --c-accent-fg: #0b1020;
        --shadow-sm: 0 1px 2px rgba(0,0,0,.4);
        --shadow-md: 0 6px 24px rgba(0,0,0,.4);
        --shadow-lg: 0 12px 40px rgba(0,0,0,.5);
    }
}

html { color-scheme: light dark; }

body {
    background: var(--c-bg);
    color: var(--c-text);
    font-family: var(--font-sans);
    font-size: 16px;
}

.muted { color: var(--c-muted); }

h1, h2, h3, h4 {
    line-height: 1.15;
    font-weight: 700;
    letter-spacing: -0.02em;
}
h1 { font-size: clamp(2rem, 5vw, 3.25rem); }
h2 { font-size: clamp(1.5rem, 3.5vw, 2.25rem); margin-bottom: var(--space-3); }
h3 { font-size: 1.2rem; }
p  { line-height: 1.6; }
a  { color: var(--c-accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Buttons */
.btn {
    display: inline-flex; align-items: center; justify-content: center; gap: var(--space-2);
    padding: 12px 22px;
    border-radius: var(--radius-sm);
    font-weight: 600;
    text-decoration: none;
    transition: transform .15s ease, background .15s ease, color .15s ease, box-shadow .15s ease;
    border: 1px solid transparent;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn-primary { background: var(--c-accent); color: var(--c-accent-fg); box-shadow: var(--shadow-sm); }
.btn-primary:hover { background: var(--c-accent-hover); }
.btn-secondary { background: var(--c-surface-2); color: var(--c-text); border-color: var(--c-border); }
.btn-secondary:hover { background: var(--c-surface); }
.btn-lg { padding: 14px 28px; font-size: 1.05rem; }
.btn[disabled] { opacity: .5; cursor: not-allowed; transform: none; }

/* Skip link */
.skip-link {
    position: absolute; left: -9999px; top: 0;
    background: var(--c-accent); color: var(--c-accent-fg);
    padding: 10px 14px; z-index: 100;
}
.skip-link:focus { left: 8px; top: 8px; }