EvoTD – by @akx / akx for Ludum Dare 24.
Started on Sunday August 26, 10:12 GMT and released roughly 9 hours later.
Works on modern Chromes and Firefoxes.
Source. Full locally playable download w/ source.

Some protips:

• Your goal: Don't let enemies (they spawn in the spawner on the left) get to your Core (the green thing on the right). Do this by placing towers to stop them.
• The enemy also evolves.
• It's usually not a good idea to sell your towers.
• Mutations may happen even when [C]loning your towers.
• The enemy really rages if it can't find a route to your core.
• This game makes no guarantees of even trying to be fair. Remember: Dying is fun. And who knows, maybe next time your starting gene (tower) pool will be more awesome.
• A "?" on a tower means it hasn't acquired an enemy. A "R" means it's busy reloading.
• You may also hit A to pick up the first tower in your tower tray for placement.