/* Design tokens. Contrast ratios are against the page background unless noted. */
:root {
    /* Colour */
    --colour_navy: #1F2A44;          /* 13.3:1 on ivory */
    --colour_navy_deep: #141C2F;
    --colour_ivory: #FAF7F0;
    --colour_stone: #E9E3D6;
    --colour_ink: #23262B;           /* 14.2:1 on ivory */
    --colour_slate: #5B6472;         /* 5.6:1 on ivory, 4.7:1 on stone */
    --colour_brass: #A8843A;         /* decorative only */
    --colour_brass_light: #D4B36A;   /* decorative on navy */
    --colour_focus: #2F6FDE;
    --colour_focus_on_dark: #8DB1FF; /* 8.0:1 on navy deep */
    --colour_error: #A12A2A;
    --colour_success: #2E6B3F;
    --colour_border: #767C88;        /* 3.9:1 on ivory, for form controls */
    --colour_rule: #D8D0BF;
    --colour_on_dark: #FAF7F0;
    --colour_on_dark_muted: #C5CAD4; /* 10.3:1 on navy deep */

    /* Type */
    --font_serif: "Cormorant Garamond", "EB Garamond", Garamond, "Times New Roman", serif;
    --font_sans: "Source Sans 3", "Source Sans Pro", "Segoe UI", "Helvetica Neue", Arial, sans-serif;

    --text_small: 0.9375rem;
    --text_body: clamp(1.0625rem, 1rem + 0.2vw, 1.125rem);
    --text_lead: clamp(1.1875rem, 1.1rem + 0.35vw, 1.3125rem);
    --text_h4: 1.125rem;
    --text_h3: clamp(1.5rem, 1.35rem + 0.6vw, 1.75rem);
    --text_h2: clamp(1.875rem, 1.55rem + 1.3vw, 2.5rem);
    --text_h1: clamp(2.5rem, 1.9rem + 2.6vw, 3.875rem);
    --text_quote: clamp(1.5rem, 1.3rem + 0.9vw, 1.9375rem);

    --leading_body: 1.65;
    --leading_heading: 1.15;
    --tracking_caps: 0.24em;

    /* Space */
    --space_2xs: 0.25rem;
    --space_xs: 0.5rem;
    --space_s: 0.75rem;
    --space_m: 1rem;
    --space_l: 1.5rem;
    --space_xl: 2rem;
    --space_2xl: clamp(2.5rem, 2rem + 2vw, 3.5rem);
    --space_3xl: clamp(3.5rem, 2.5rem + 4vw, 6rem);

    /* Layout */
    --width_page: 71.25rem;   /* 1140px */
    --width_text: 45rem;      /* 720px */
    --gutter: clamp(1.25rem, 0.8rem + 2vw, 2.5rem);

    /* Shape and motion */
    --radius_s: 2px;
    --radius_m: 4px;
    --rule_thin: 1px;
    --rule_accent: 3px;
    --focus_ring: 3px solid var(--colour_focus);
    --duration_fast: 150ms;
}