McPixel has a special Pay What You Want promo going on this weekend only. The minimum donation amount is $1.
There’s a Steam Greenlight project for the game so vote for it to get on Steam.
If you want to try out the game first the dev is actually encouraging people to download the torrent off the pirate bay. Give it a go and if you enjoy it; donate money later. There’s also a web based demo that you can try out.