I'd forgotten this even exists....
I remember liking it, back in '89, not sure how the game play would hold up today.
Game play is you jump around cleaning up infected squares, so you can destroy these stones, the stones must be connected by unbroken tracts of uninfected squares, once all the stones are destroyed you have a short time to navigate to, and destroy an obelisk.
but there are these plants that move around and re-infect as they traverse.
once you clean up one island you move on to the next one.