Goal: Guess the secret code of four colours (chosen from six).
Win: Get 4 greens.
Limit: You have 12 tries. If you don't solve it, the code is revealed.
How to play:
  1. Tap a colour, then tap a position in the row to place it.
  2. When you're ready, press CHECK.
  3. Your guess moves up with feedback shown:
    = correct colour, correct spot
    = correct colour, wrong spot
    4. -> BACK