Challenge
I focused on WCAG 2.x AA criteria that are most relevant to dense, card-based layouts on mobile: 1.4.11 Non-text Contrast, 2.5.8 Target Size, 2.4.7 Focus Visible, 1.4.10 Reflow, and 1.3.1 Info and Relationships.
The Web Content Accessibility Guidelines (WCAG) require that:
Visual information used to identify UI components and their states have a contrast ratio of at least 3:1 (except for inactive components or when the component is determined by the user agent)
Pointer targets be ≥ 24×24 CSS px or have equivalent spacing, kept clear of platform gesture areas like the iOS home indicator
Information and relationships be conveyed consistently in both visual layout and programmatic structure
Content reflow at 320 px width / 400% zoom without loss or two-directional scrolling.