Feedback is a further crucial component of climate models: the accumulation is affected by the current value of a quantity. Again, there are simple examples in physics to draw on, such as terminal speed and cooling curves, both of which exhibit negative feedback.
Feedback can be positive as well:
The resources are there to support an exploration of pre-built models, with the structure of the model explicit. What's more challenging is to see how such models might be constructed live in classrooms by teachers or children. There is still work to be done to provide suitable building blocks for models (with fruitful constraints on the assembly of such blocks).