Very addictive good tower defence - perhaps a bit too easy though.
I had no trouble keeping the spaniards at bay in my first attempt - until the game got stuck - I tried to place a unit on the bottom row and the menu for the 3 units types appeared but clicking the units or the X didn't do anything.
The graphics were very thematic and nicely animated even down to the different speeds for the heads bobbing. Loved the horse animations.
I just noticed the bug above fixed itself by me switching to this tab and then back - it relocated the unit choice window up a bit.
Could maybe include enemies that kill the defence units - that would make it harder.