This game is awesome, it needs some polish to (you can't unselect unless you go back to menu in the top for buildings, on tablet in chrome the building info often gets stuck on screen, ...).
With the added strategy through characters this game would be great with fog of war on the enemy half side of the map and a multiplayer.
Did you take inspiration in some other tower defence game? This the first time for me playing one like this, love it!
Will you be pursuing this further?