I think either AABB collision test or circle-circle is sufficient for your needs. Usually it is not necessary to have perfect pixel level precision in determining whether 2 objects hit.
For circle-circle, have all your objects have a center x,y and a radius r; to determine whether 2 circles overlap: test (obj1.x-obj2.x)^2 + (obj1.y-obj2.y)^2 > (obj1.r + obj2.r)^2
For box, have all your objects have x,y, width and height, and check whether the box overlap in x axis and y axis.
Edit: In case that you really really want to use triangle - polygon level of precision, you need to first implement/find a intersection test for lineSegment vs lineSegment. Then for the intersection test between 2 polygons, test whether any combination of their edges intersects OR whether one object fully contains the other (point in shape test).