Nice poster. You should have put the names on the achievements, instead of just numbers.

You made another GREAT GAME ! And being a shark never gets old. Thank you !!!

On the good way!

In order to make your game better, you should make some minor modifications:

-direct the UFO flames towards the tank:
var flamedir = Math.atan((tank._y-ufo._y)/(tank._x-ufo._x));
flame._rotation = Math.round(flamedir*180/Math.PI);

-Make an explosion when the tank is hit by a flame

-Maybe there is too many planes to kill before reaching the next level. I think 100 would be enough.

-And to finish, make a better user interface with nicer fonts and buttons.

Good job man!