I enjoyed playing your game and it is very nice.
But as it is a game, you should focus more on UI and make it colourful.
Here are some of the things that you can do:
- Hide Title bar and status bar to make it fullscreen.
- When on Main Screen, I am not been able to close the app; the Main screen automatically starts again when back pressed.
- Use images for buttons
- Big and custom fonts
- Background images with background music
- Good placement for ads. (Ads shows up in the middle of the screen)
BTW, how did you make cards to animate?