This is an awesome concept for an idle game! To make it even more engaging, I’d suggest expanding the variety of upgrade options, especially early on. For example, introducing special upgrades like a Magnetic Peg that pulls nearby balls or a Splitter Peg that duplicates the ball would add a layer of strategic depth and excitement.
Right now, if the first 1–5 levels only offer a few upgrade choices, the gameplay risks feeling repetitive. Players with shorter attention spans (which is most of the mobile audience) could lose interest quickly. By introducing new mechanics, peg types, or visual evolutions at a steady pace, you’ll keep the experience feeling fresh and give players something to look forward to achieving.