Thanks stmav. Anyone who downloads please leave feedback here or in a review. I'd really like to know what you think and can make any changes you guys believe I should.
I've not played it myself, but a couple of likely reasons:
1. The paid version doesn't offer a big-enough incentive over the free version.
2. You don't have a link to the paid version in this thread.
3. It's just not a game people find to be worth a purchase.