I'm sure there is a reason for this. But it indeed is something OP may want to consider. Gingerbread is almost 50% market share.

Source: http://developer.android.com/about/dashboards/index.html

As simple as the graphics are, I'd wonder whether it couldn't have been done another way. You're definitely right, not targeting 2.3+ is kind of a big deal.

The game is very decent, though; runs very well on the Nexus 7, solid gameplay, nice mechanics.

It was originally supposed to support 2.3+, but due to timeline constraints I had to release it as 4.0+. I'll be looking into 2.3+ for a future release though!

What was missing in 2.3 that made it non-compatible?