A "Speed Game up" button would be most useful on the Infinite waves setting. It gets rather boring watching your defenses destroy another wave of peasants with no problem.
Interesting Challenges? Okay, so the heal block presents a slight conundrum, but, so far, I have had no trouble telling my own blobs from my enemies. This is partly because, except for my main orb and any permanent shadow orbs, I can't really tell where my shadow orbs are.
With the aforementioned health carry over problem, the game has a great concept, but punishes players who finish levels quickly. I, for one, do not enjoy staring at an unchanging computer for the 10 minutes it takes to heal. 3/5
My biggest problem is that I start each level with the exact same life I ended the last one with. This means that even though I have been pumping strength for who knows how long, my health almost never goes above 60.
After that list of warm-fuzzy comments, I feel like a troll saying that this game is kinda lame. I was barely surviving until I grabbed the gattling gun, at which point I barely put any effort into staying alive.