My life stopped for three days, awesome work :D Glad there are only so much levels of progression, can get back to living now xD
Speed multipliers are top-notch addition, I think now the top of the row improvement would be showing required wave/element level on the tower level up button so that hovering is not required, second most wanted is probably 0-delay hover tooltip on everything
Hope you guys take the learning and do something of your own after this, perhaps in steam ^^