It's cute and fun to play like TANS's original. It seems a bit more difficult to play than the original. When I posted a test version in the #gamedev chatroom, people were getting up to levels 10 and 15 without much trouble, so I added a bit of code to make the blocks get more dense as the game goes on. Around level 20 the level should be half the width of the screen and 20% of usable screen should be full of blocks, so it should be durn-near impossible by then.
Game Design Hint: If you're making a game that doesn't have a clear completion point (like "Zelda") but just goes on forever (like "Pac Man"), figure out a point where the game should be impossible to play rather than having the difficulty "level off" somewhere.
Also take into account people not playing the game the way that you'd play it. This was a problem that Zap Pod had originally. The object of the game is to shoot ten rocks to move on to the next level while avoiding the other stuff attacking you. Problem is, the level itself doesn't get more difficult as time goes on (i.e. level 2 is more difficult than level 1, but level 1 keeps its difficulty). That means that if you avoid the rocks rather than try to shoot them, you'll stay on level one forever without the game getting more difficult. Version 1.1 of the game makes the individual levels get harder over time, so you've eventually gotta shoot all the rocks and progress, or else you're doomed.