Very cool idea. Brings back memories from build-your-own pinball videogame I played on my cousin’s computer in the late 80s in monochrome graphics. The idea is cool but the fun is to have freedom to build and then play. Getting only one piece at a time seems a chore. I’d make pieces that have tradeoffs to add and let players decide how to build their boards. Some social features around sharing boards and high-scores would be pretty cool too. Great start!