https://shiftyjelly.wordpress.com/2011/08/02/amazon-app-store-rotten-to-the-core/, posted 2011 by peter in android business opinion scam
Amazon’s biggest feature by far, has been their Free App Of The Day promotion. Publicly their terms say that they pay developers 20% of the asking price of an app, even when they give it away free. To both consumers and naive developers alike, this seems like a big chance to make something rare in the Android world: real money. But here’s the dirty secret Amazon don’t want you to know, they don’t pay developers a single cent.
Apparatus is a sandbox puzzle game for Android devices. Use your hammer to pin planks and wheels together to build anything you can imagine, connect your apparatus to motors and give them power using batteries.
Admittedly, I haven't tried it, but it looks like a lot of fun and I really like sandbox games. I almost wish I had an Android device now.