Hello Avocado Smoothie, these sorts of games are always more motivating to play the more there is to unlock. Having said that, given the scope of this initial game and your feedback requests, making suggestions for further additions probably isn't useful. Aside from the wonderful suggestions above, here are some things for your consideration that might help with motivation:-
- Adding some other numerical values: displaying the amount of gold earned (in the location where the coin previously was) when it is collected alongside the jingle; displaying the current and maximum values of the water trough, as well as the increment gained when upgrading or refilling it.
- Adding some additional colours, jingles, etc, to the purchases. I noticed that when eye concentration is intently focused on the field, it removes focus from the shop window. Doing something such as changing the highlighted colour in the players periferals or playing a short sound to show something can now be afforded could be beneficial. A different approach would be to show the amount of coins where the water trough level currently is, and instead show the trough level in the shop window. This would make the more valuable information more prominant. The solutions are numerous, as you wish.
Triggering dopamine is king!