That's Tundra Defense, and it's pretty awesome. The major advantage it's going to have over HF is that objects in TD can be placed anywhere, while HF follows a much more linear, set-piece design. I was beginning to suspect that we'd see HF for PC soon when all the TES titles went on sale the other day. That's the name! I have a good but short memory. I thought the same when I saw TES titles on sale. Lucky we was right. :)