1) mark empty plots as such - it gets annoying keeping track of which of the 20,000 holes on my screen still have something left in them. 2) put screen boundaries - blasting those 0.25-ton gold chunks off-screen is rather annoying. 3) with suggestion #1 in play, the slow explosions stop being necessary and you can add a "skip" button to them
how do you tell which upgrades you already have? the "don't need to buy" display is sporadically wrong... some sort of UI representation (different colored text?) would have been super-nice
a shooting game where shooting someone in the head from 10 yards doesn't kill them, but at 5 yards it does? while this can be seen as more "realistic", this doesn't allow me to perfect my awesome sniping skills, and isn't all that much fun.
graphical glitches make some levels unplayable - random white rectangles block out most of the screen. end-of-level screen is also whited out (if this happens to you, you can click around, you'll eventually find the invisible Next button)
SERIOUS drawing bugs - buttons don't appear until moused-over, trade window is invisible (but can be painted by picking up an item from it and waving it around - putting the item down makes it invisible again), etc.
"Your girlfriend is upset because you haven't spent time with her in weeks" - girlfriend faction goes down, sponsor faction goes up! why don't they want me to have a life!?
would be nice to be able to permanently set my team's color - it occasionally gets confusing when i play 50 games in a row as blue and suddenly i'm playing *against* blue
4 maxed (any tower) spread over the map totally dominate everything. considering i can build these by wave 12-15 and the levels have way more, that should tell you something (and no, it's not "players have too much money")
selecting opponents is a bit painful when they're right on top of each other - e.g. a bat is in front of a tongue monster, so i can't select the monster easily
 "Boom Town"){kind=icon}
 "Utopian Mining"){kind=icon}
 "Pirateers"){kind=icon}
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 "Relic"){kind=icon}
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 "Armed with Wings 3"){kind=icon}
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 "Darkness Springs Chapter II"){kind=icon}
 "Tyrian: TD - Level 2"){kind=icon}
 "A Short Journey"){kind=icon}
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 "Pirates of the Stupid Seas!"){kind=icon}
 "Commando Defense"){kind=icon}
 "Immortal Souls: Dark Crusade"){kind=icon}