What Works

• Basic HTML5
• CSS2.1 + limited CSS3
• Flexbox (with prefixes on older WebKit)
• @font-face (but don’t use — system font is faster)
• Simple JS (form submissions, basic DOM manipulation)
• HTTPS (required for some features)

What to Avoid

• Animations, transitions (ghosting on e-ink)
• Gradients (banding on 16-level grayscale)
• Drop shadows, blurs
• Web fonts (slow to load, use system serif)
• Heavy JS frameworks (React, Vue — too large)
• Images with fine detail (e-ink can’t render well)
• Dark backgrounds (e-ink inverts poorly, use #fff)

Kindle CSS Design Principles