So, I don't know the programming, but here's some thoughts.
You run around the field grabbing cabbages.
The Cabbages gradually respawn.
Occasionally a tainted cabbage appears and if you grab one you die/get stunned.
The tainted cabbages stay as obstacles.
The fiend of the ninth cabbage follow you and you have to avoid him.
The fiend can't move through healthy cabbages and so can only follow your trail.
There are more and more turtles in higher levels.
They initially start trapped by the cabbage but if there are empty spaces adjacent, they move randomly around as obstacles.
The fiend can't move through turtles either.
You run around the field grabbing cabbages.
The Cabbages gradually respawn.
Occasionally a tainted cabbage appears and if you grab one you die/get stunned.
The tainted cabbages stay as obstacles.
The fiend of the ninth cabbage follow you and you have to avoid him.
The fiend can't move through healthy cabbages and so can only follow your trail.
There are more and more turtles in higher levels.
They initially start trapped by the cabbage but if there are empty spaces adjacent, they move randomly around as obstacles.
The fiend can't move through turtles either.