Tooltips for those upgrade buttons are being added as I write this. A split peg is a %chance for a ball to double itself when it hits any peg.
I think there are a few ways we could approach this as I have definitely had Split Peg get really overpowered in certain runs.
Boosts and buffs are coming in the next version! Some things might get a little slower, but I'm hoping for a greater impact of upgrades overall, as well as a global upgrade shop across all levels/playthroughs. That would come with a prestige system.
Your feedback is awesome and super appreciated. We'll take a look at these multiplier ideas and see if this works!