Not sure if this would work but here it is anyway. Dd4.5 also loves to invent and build. Instead of buying expensive kits, we collected two build-a-bear boxes, other packaging boxes, toilet and kitchen paper roll tubes only, duct tape, and glue. No instructions- just have fun. Dd built a game with an incline in a box and cut a hole and made up a game where you roll the marble, make it roll back after hitting the edge of a box wall and fall into the hole- you win! It was pretty engaging even for adults. Then she built ( this one with my help) a long inclined tube, hid it in the box and you roll marble from one end to collect from another. She even taped a funnel to collect the marbles on the other end so clean up would be easy.
I don't know if my post is even making any sense.
