Some progress:

• Prototyping UI elements (_TK_ is working on skins)
• Building selection, placement, upgrading, and repairing
• Very rough numbers pass on buildings - price, population requirements, HP, etc. Won't know how well these numbers work until the battle portion of the game is working. (You can see the spreadsheet for this here, if you're interested)
• Transitions to and from battle mode
  

Coming up:

• Buildings will have guns. You'll be able to aim them in build mode.
• Battle mode. This week, I'm going to focus on getting battle mode working. Waves of enemies will appear, and you'll be able to shoot them. They will shoot you.
  

Once the game has a working battle mode and win/lose conditions, I'll start posting builds! Until then, here's a development screenshot: