Thanks for the feedback!
For the sound - I wasn't able to produce any meaningful/fitting music that doesn't nuke the 3kb limits.
I agree the gameplay is a bit lackluster and not well balanced - should have put more thought into that!
Regarding the file-size ; I wasn't entirely sure whether the compressed TAR archive has to fit into a QR code or the uncompressed files thus I had to remove all spaces since each takes away 3 bytes w/o compression.
The PNG file is both a mixture of Tiny-PNG and own compression so thanks for the compliment ;P