Flawed game design
Aesthetically, your game works with it's simplicity. The fluid stick figure against a simple background works easily. The old adage of 'simpler is usually better' often works depending on the message and design of the game.
Code-wise, there seems to be problems with hit detection while moving, and with a precision timing game like this, precise hit detection is mandatory. Standing still and moving inch-by-inch is fine, but for some reason when moving at high speeds you'll get killed by attacks far off. Perhaps your image size is becoming wider thanks to the lower profile and moving arms and legs; clipping a limb shouldn't be that disaterous; there are some points where two narrowly placed blocks should have enough room in between them based on the stationary figure's size but don't while moving (it's inevitable to hit on or the other).
In addition, some blocks will kill you if you hit them from the side as they are on the ground, while others will just knock you down. This inconsistency makes for more trial and error and less skill or reflex. If this is being done intentionally, note that trial and error promotes less interesting gameplay while reflex and skill-based games promote more, so try for skill over memorization and trial; if it's accidental, try going over your code.
In terms of overall concept, I'd have to disagree. When going for aesthetic simplicity, it's a good idea to create gameplay with depth and high levels of interest; whereas simple gameplay should be pleasing aesthetically or be fueled by motivation. Having both an oversimplified game and a lack of anything aesthetic or motivating (like good art, story, or game enhancements) usually results in a game that people will try only a few times. After all, there is no real motivation, whether story-wise or whatever, to continue to play the game, and the game is simple enough anyways that no real fun can be attained actually playing it. Add that to the extreme level of difficulty, and, well... you're looking at two attempts, max, before the average player gives up.
You may think me or others are just trolling about the difficulty; we're not, at least not exclusively. There really is no motivation to play this game, other than maybe those who want to say they beat it. In terms of difficulty, I'd say annoying rather than challenging. You're not challenging the player at all; you're just pissing them off. Instead of designing a game based off of reflex or decision-making or multi-tasking, you're designing a game based off of failing until you succeed, which not only isn't fun and doesn't help pass the time (which, I'll be honest, is all newgrounds is), but doesn't encourage players to play it.
You'll want to introduce game concepts much slower. Not only will this increase total length, but it will make the learning curve actually fit on the graphing paper. As it stands there is nothing to learn, just a wall of death to stare at for eternity. Added to that, though, is for you to actually have game concepts, and interesting ones at that. Only moving forward is a start in the originality department, but falling blocks? There goes the novelty. Zombies were okay, but again... slowly; so on and so forth for the others. There has to be something else to your game though, and to implement such would be difficult, hence why (or partly why) I say your overall game design (or concept, I guess) is flawed.
With control comes multi-tasking, with a complex game comes decision-making, and with precision comes reflex. Your game is bad in all three areas, making it less of a game to be enjoyed and more of a game to be endured, because the player just doesn't have the tools to succeed consistently nor has the interest to care.
Yeah, a troll rant, per se, but to each his own, right?
