My son keeps coming back.
My girls have been very linguistic, academically inclined, early readers (one VERY early), etc. My boy would rather find something to climb and jump off of. His world and approach to logic are very, very different! It's been a challenge to find apps that he can figure out and also enjoy, but this is one he comes back to time and again. At first he played without purpose but now he understands it a lot more and enjoys the fast finish on the learning pieces of this app.