Level 20

The premise of the level is that all the triangles are arranged into pairs, and that after clicking a triangle, clicking its paired triangle is the only way to make them both yellow. The album below shows the pairs of triangles, and an efficient route to complete this level in a speedrun, despite the fact that it may not be the best route.
https://imgur.com/a/frFng

Level 21

The fastest way to do this level can be found right here: (taken from my 5:59 run)
https://youtu.be/YfROsHLtM5U?t=127

Level 23

why the hell has no one made this

anyways level 23 has a windmill style <sadegbean method>

https://youtu.be/ACWWAP-imEU?t=222

saves like 1-7 seconds <if you were me and spammed the squares and hoped to finish>

ok

Level 40

Level 40 is a bit more complicated than level 21, the reason being that there are 4 circles instead of 3. Here is the best way to do level 40: (taken from my 5:59 run)
https://youtu.be/YfROsHLtM5U?t=237

Level 41

Best strat I've found, but probably somewhat improbable.

https://youtu.be/zoD1PP07a5c

Update: 14 taps appears to be the fewest possible (the video shows an 18-tap solution iirc). Further research into the best possible arrangement of 14 taps may be desirable.

optimal 44

I don't know how to add an image so here's a short video. You only need to tap the 6 spots shown 2 times each. It does not matter what order it's done in.

https://youtube.com/shorts/FruqKKa4TWQ?feature=share

Name	Author
Level 20	Deleted 7 years ago
Level 21	ozelines 4 years ago
Level 23	riin 3 years ago
Level 40	ozelines 4 years ago
Level 41	Eiim 4 years ago
optimal 44	sadgebean 3 years ago