Hello integral of tan x dx,
I know this is a very old thread, but I've solved all 3 of the levels. My replays are attached. Overall, your brother did a great job on this!
The first level was surprisingly difficult, although I have a stacker leftover and simply resorted to a timing heavy solution
The second level should be a very bad backroute, and I find it really surprising that Icho missed this solution entirely
No skills required (no pun intended)
Finally, the third level was my absolute favorite in terms of what's on the screen (the quadratic formula, a quadratic equation with solutions x = 1 and 2, pi, etc), being a math person and math teacher myself. This one was quite hard for a builders only level. Took me a while.
I'll take a look at your Integral Lemmings pack soon!