I assume this is more a project you are working on to develop your game making skills. And that you put it up to get some feedback more than anything. So here's my feedback. Competent game that badly needs some better art. I think it also needs some power up of some kind. My suggestions, a speed up power up to get through the tricky part. And some kind of ability to shoot in a different direction then you are traveling because its really annoying to have to turn around to shoot at what is chasing you.

Not bad, could do with a touch up though meaning adding more options persay like a mute button maybe some music wouldnt hurt.
If your down to adding things maybe change the colors of the squares every now and then, even adding some upgrades for fasting shooting etc, also add a campaign esq with added classic mode(aka this game as it is now) but who knows
you have potential.

This is not bad for a first game submission, but it could use some features that could keep the game interesting. Here are some suggstions to think about if you want to submit an improved version of this:

+Provide keys that are devoted to aiming/driving the Triangle "Tank" diagonally. Also consider providing the player the ability to select which keys are used for which directions and actions.
+Revise the scoring system to award extra points for consecutive hits without missed shots, consecutive kills without taking damage, or both.
+There is no real objective in this game, save for surviving as long as one can and killing as many targets as one can. Objectives provide the player a goal to win, or at least move on to the next round. Here are some examples of objectives:
-Kill a set amount of targets, whether general or specific targets, with or without time limit.
-Survive for a set amount of time.
-Prevent the enemies from reaching a certain area within a set time.
+Currently, the opposition slowly and blindly marches toward the player, setting itself up as cannon fodder. Increase the variety of enemies in at least one of these ways:
-Enemies with increased speed will force the player to react faster.
-Enemies with more hit points will draw the player's attention longer.
-Enemies with a more random movement will be harder to hit.
-Enemies that fire shots force the player to move to avoid damage.
+If stronger enemies exist, then the player should be provided a variety of weapons and powerups, such as the following:
-A more rapidly firing cannon can more quickly defeat enemies, especially those with more hit points.
-A cannon that fires multiple shots at once can wipe out swarms of foes.
-A cannon that fires more damaging shots can defeat enemies in fewer hits.
-A cannon that launches larger bullets has more room for error against randomly moving enemies.
-Healing units allow the player to survive longer.
-Upgrades to the Triangle Tank, such as speed, can also further help the player.
+The battlefield is currently a wide open rectangle. Adding obstacles that impede movement and/or block bullets from both the player and the enemy will add strategy to the game.

Meh...Isn't totally unplayable, but it's really simple and the controls kind of suck.