Snake is hard to spot — color it classic retro green #2

Problem

The snake currently renders in #f4f4f5 (near-white), which blends against the light foreground text on the dark background. It's fine but visually boring for a snake game.

Expected

Classic arcade feel: use a vibrant green for the snake body, e.g. #22c55e or similar. Keep the head distinct if there's already differentiation.

Scope

• Update index.html (styles / render logic for the snake cells)
• Keep the dot-grid background + layout intact
• Please include before/after screenshots so the visual change is obvious