You made tetris into a gambling game.
Why?
I never liked tetris, but this is kinda fun. As a person that tends to take risks and shoot for the titular 4lines, i felt like the reward wasn't quite on the same level, feels like the mults could give more since the upgrade costs climbs very steeply while not giving a lot of return.
Also hiding the upgrade tree feels very frustrating in this, since you have to travel through the same 5 colors only to get the same zombie upgrade which is totally pointless.
More mechanics are needed. There's a solid gameplay loop right here but needs actual balance and actual mechanics, intentional and "unintentional" interaction.
Finished the playtest with about 5 lucky tetrises basically. Good but way too little content right now with bunch of questionmarks.
Upgrade field needs to be draggable