there should be more weapon upgrades available, by the end of the final round I would have been on weapon level 47 (I counted the arrow things I collected).
desperately needs a hotkey for restart. Tapping R is far less annoying than having to either throw off your aim by clicking the restart icon or having to wait to fire off the remaining arros and wait for each to dissapear.
on challenge mode, just build steel-girder rectangles around the two hovering blocks at each end (as tight as possible), then link these to a steel-path from the beginning angling upwards slightly, again at both ends. Then just connect a series of wooden bridges to each steel-path, in a stretched u shape
the lag really needs to be sorted out, and the later levels were difficult because the game mechanics sucked and the lag was very heavy, not because it was challenging, which is what it should be.
 "Take Something Literally"){kind=icon}
 "Sharp Shooter"){kind=icon}
 "Storm the House 3"){kind=icon}
 "Caravaneer"){kind=icon}
 "This is the Only Level"){kind=icon}
 "Hover Bot Arena"){kind=icon}
 "Endless War 4"){kind=icon}
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 "Particles"){kind=icon}
 "Sonny 2"){kind=icon}
 "Amberial"){kind=icon}
 "Starcom"){kind=icon}
 "Cargo Bridge"){kind=icon}
 "Spewer"){kind=icon}
 "The Great Siege"){kind=icon}
 "FWG Knight 2"){kind=icon}
 "Shopping Cart Hero"){kind=icon}