Hi, thanks for the review.
You're right about the missing visual selection, that is something that we planned to do similar to the wallbuilding, but at the end we left out to focus a bit on the game difficulty at the end.
About the upgrades it was planned also in the beginning, but we skipped it to focus on other areas, however we slightly increased the size of the gems with each upgrade, but it can be hard to notice in the middle of a waves. :D
Sound for hurting enemies wasn't planned, but it's actually a good idea that we would do with future games with similar mechanics.
Overall, we're glad you enjoyed the game!