I just asked my students how they have felt about these courses and they responded "fast." When I asked why it was going so much faster, they said they felt it was because they just know more now.
We talked about what velocity is doing, and how it's just a replacement for a counter. However, I would be interested in exploring how putting a counter on velocity would look with changing the x variable instead (I hope that makes sense). Similar to how collisions was explored in Stage 12, Lesson 3.
Right now the biggest hangup in progression is just that the kids keeps working on and changing the games that they are building. The kids love the coin game, and they are adding enemies, walls, and all kinds of things to change it up.