Definitely enjoyed this nostalgic experience. (reminded me of playing the platypus games, thoguh perhaps it's not quite the same level of polish here :P) At first I wondered if there was also a tower defense mechanic, but once I realized it was ok to let them through, I relaxed.
Having me 'insert a coin' on loss was cute, and having the finale of combining forces was funny (ya got an audible snort from me at least :P)