The world 3 is really nice. A chance that I didn't gave up before. It's a bit sad that the first two world looks just a little boring and that's the music isn't really attractive. 4/5 simply due to the world 3.
Some levels are so hard that I need to pause the game almost every 2 or 3 seconds to check or rebuilt primary defenses. I also need to adapt my strategy for thoses maps after many loses. But I like it, cause at the end, I always find a way to win the battle ! A key to pause would be really great for those maps, and a way to sell building. (the first buildings that we really to buy at the start to survive may block us to overpass the enemy defense at the end)
For the 4songs : - 1 Near the start (you need to activate a switch in right side of the same area) - 2 Near the place where you get the wing, you need to destroy a wall with the upgraded spikes - 3 Under the big ancestor statue, still by using the upgraded spikes against the small wall. - 4 After passing the door by activating the 3 crystals, jump into the first pit, then on the left side we can see the entrance for the last song