As the last task in number challenge, I wanted to get the kids to generate the even numbers and then generalize to apply function:

Create a box with two holes, in and out.  Put the natural numbers nest in the in hole.

Using the numbers coming into the natural numbers nest send the even numbers to the out bird.

Trying to predict how kids will approach this task, we thought it is likely that they will do it by removing every other element. E.g., use dusty to suck 1, give 2 to the bird, suck 3, give 4 to the bird, etc.

The problem with this is that it is quite hard to train a robot to replicate this behaviour. A robot only "sees" the top item on the nest. It cannot operate on two succesive items in one iteration. In order to simulate the "eat one, pass one" behavior above, we have two options:

• Use a team, and a switch to pass control between the robots.
• Use a stream-splitter: a robot that forks a stream in two, There's a cute trick for doing this with a single robot.

In any case, much too complex for the level of programming our kids have mastered.

After some consideration, we decided it is better to change the task so that it deals with multiples of 10 instead:

Create a box with two holes, in and out.  Put the natural numbers nest in the in hole.

Using the numbers coming into the natural numbers nest and Tooly, send the multiples of 10 to the out bird.

Inter alias, there's still a problem with the graphical presentation of the task: the image is too dense, and its hard to understand what the robot does, and what the user is requested to do.