The two lasers can do a lot to help at the beginning - line them up well.
Having two means that one can keep firing while the other is upgraded.
Build one laser up to 7 and build the blaster up to 7 for optimum range. The laser in the top right corner needs to be lined up so that it is at the correct angle to shoot down the angled line as the critters move away from it.
Add more blaster towers and upgrade them to 7.
Now we've added a missile tower at the bottom left. Get it up to at least level 5 which means each bomb is not wasted. Level 6 is best but don't go to level 7 as it's too slow.
Another missile tower. Get them all up to level 6.
This is what we've been working towards. Plenty of shock towers as the critters get very fast towards the end.
This is when it gets fun.
Level complete with no loss of life.
