1.64 Euro earned in six months with one game

Published my game (link at the end of this post) 6 months ago on Google Play without ads.

Also published on Amazon Appstore, because Amazon was promoting its ad network and gave new developers $100 to spend on advertising.
Those $100 brought me ~75 downloads (meh, i would never advertise on Amazon using my own money).

Here are the statistics after 6 months:

Google Play: 31 current installs, 102 total. (No ads).
Amazon Appstore: 77 total (can’t find where to check current installs, amazon dev console isn’t great). (Displaying ads: Admob banner and interstitial).

Link to my game:

I can be wrong, but I feel the game is not bad, it just lacks visibility among thousands of other games.

Will be grateful for any ideas of how to get more downloads for my game.