A while ago I was casting covetous gazes at this cartridge priced at £20; at high that price it's a must!
Multitudinous monstrosities are pouring out from their burrows and heading pell-mell towards a throbbing generator. They want to munch into the walls costing you a life if all the walls are consumed. Blast 'em? Oh, you don't have a laser. Instead you will have to become adept at manipulating horizontal and vertical bars in order to shove them off the screen. Use your cunning to guide one of your purple mutant-hunters down one of their tunnels and flip immediately to screen two. Strangely, he's turned blue, but no matter: steer him down the ladder, dodging into side chambers to avoid falling rocks, and place a bomb near the queen mutant: zip back to the surface and detonate. You're back to screen one but with only three burrows to worry about instead of four. Unfortunately the bars have developed gaps so the task doesn't get any easier. To move up a level naturally all the tunnels need eliminating.
Considering the mutants have to be small, the graphics are good while the sonics should motivate you. Different. I like it!