(I am now in a rush to test as many games as possible to help, so please do not mind the cursory reviewing style.)

1. The concept seems interesting!
2. Controls are QWERTY-only instead of layout-independent (I have an AZERTY keyboard), BUT arrow keys are enabled; still, I feel like this is an error (like, default controls not disabled), because then, the movement is slower, with more inertia, and unanimated.
3. The visuals are quite prototypical; and this is fine with me, even though you did not draw the sprites: programmer art all the way. ;)
4. Small misspelling on game page: "you task" -> "your task"
5. Wow, my AZERTY controls give me a really hard time playing… :o (Plus the stun gun delay issue, see below.)
6. I would suggest adding sounds, especially the gun sound as sparklewing wrote. Sounds give life and important player cues to your game, do not underestimate it!
7. Totally agree with rodasFodas about removing the stun gun delay, and allowing shooting (although solving the first issue might already make the game playable enough and more interesting without the second point! This needs testing).

Sorting playability would already be a huge step ahead; I think you could then add some variety, for example, obstacles, or/and different types of enemies. My takeaway from this game is the concept, it could be a very interesting (non/semi-violent! XD) action/puzzle game. :)

(By the way, just putting here that my game is pending until I get the submission form.)

PS: testing just some more, I realize that a stunned enemy actually continues to go straight along the same direction! Which is an interesting mechanic, actually: first lure them, then stun them, and only after go for the cube. Which makes you move more, but in this case, allowing up and down fire would help. So, I think you could keep this ‘inertia’ mechanic and extend firing directions. Some animation of the enemy (whirling, for example) would greatly help understand his state! :)

Also, possible bug: at one point, firing again on some stunned enemy apparently made him disappear.

The idea of using a stun gun to numb the enemy is not seen in many other games and is a good, original idea that meets the limitations.

I think it will be better if there is a sound to increase the taser-like effect. It would also be nice if enemies who are hit by a stun gun would stop instantly. Good work!

tricky game but fun and I like your concept with the stun gun! nice one. 

Great game in general!

However, there are a few bugs that need to be sorted through. If the energy cube is pushed to the very side of the page, you will find it very unpleasant to move it back out.

Overall, pretty good game!