Sensei, that puzzle in 19:46 was indeed the hardest, but basically, if you number the tiles, like so --- 1 2 3 4 5 6 7 8 ? Combine the image of 1 + 2 and remove the overlapping lines and you get the image in 3. Combine the image of 4 + 5 and remove the overlapping lines and you get the image in 6. The same if you combine the image of 1 + 4 and remove the overlapping lines and you get the image in 7. So, if you combine the image of 3 + 6 (or the image of 7 + 8) and remove the overlapping lines, you get the answer for ? which is upside down L and L. (Yes, it was a difficult puzzle and it took me awhile to solve that too. You need pen & paper to manually draw it and figure the answer out. Glad to see that you've figured it out.) Anyways, thank you for playing this, sensei. XD I appreciate the time you gave, especially when the puzzles were challenging. As for that ending, I guess you can say that it's both a good and a bad ending, since your character saved her sister by switching with her.