Love this game! So addictive. I also think I've found a bug. If you:
1. Get to an upgrade screen.
2. Click on a "Wildcard" you've acquired previously.
3. It will detect it as a valid "upgrade" when it's not (presumably).
4. Then the following screenshot will show (entire deck is available for selection).
Above bug aside, love this game! The design is addicting and thank you for making it <3