I know how you feel, I was stuck on this level forever. There is a link to a walkthrough on the official twitter now. This helped me pass some of the later levels. Its at twitter.com/bloonsiphone.
Under the lid was a tough one for me but i figured out that if you get the dart to go over the wall JUST BARELY it will work. I had to do a lot of resetting for that level. I got a shot of the angle not sure if it will help that much because its hard to get a good shot (level ends almost instantly) but i will post it just in case.
I agree its tough to show the angle! It just takes plenty of practice and eventually you will get there. Needs a pretty precise shot though. Theres a video on youtube aswel for this level but never really helped me.
Can someone show a picture of the angle and power of the Boomerang shot on level 40 of the level pack 2?
I finally beat all 100 levels!! It was hard even with endless darts. When you beet level pack 1 or 2 you unlock a secret level which is cool
I have a idea of how to beat it now. Hit the top one, let the spikeball bounce for a little and then hit the sabre to drop it... just need perfect timing.
I see when the spikeball bounces it gets a bit higher then super low, then higher.. etc till it goes away. I think you have to get it perfectly when it goes super low bounce, hard to explain it lol.
For pack 2 level 42 the spike has to bounce 5 times before you hit the sabre and make it fall then it will clear the rest. Check the walkthrough I posted earlier it has a guide for both level packs.
alright finally beat it.... Get the dart at the bottom first. Shoot the spikey thing, let it bounce about 4 to 6 times. Then shoot the sabre on the 4 to 6th bounce.