Um well.. i don't think it's about earning money but about getting the customers inside the shops. at least i never saw a rise in goal-percentage when customers left a store when no other customers were around anymore...
Reminds me of another game i played some years ago. was just the same...
strange thing: when finished it says "snow cast", the game i played back then was like this one, difference was it actually was with SNOW instead of sand.
found a bug:
clicked on "poison tower" on the right side, after that i selected an already build fire tower, upgraded the fire-tower and ended up having 5 gold, but i could still build the poison tower, ending up with -gold...
Oh BTW, Just to have that noted - i can't get the medium or easy badge, altho i won being insane with a 29dmg shot... yup, i was logged in, an the chat showed a green light.
played it twice, 2.1xx.xxx was my highest. 80 combo.
running the game without playing it right now, just for that awesome piano-track...
kudos to the pianist!
 "Hedgehog Launch 2"){kind=icon}
 "Shopping Street"){kind=icon}
 "Desktop TD Pro"){kind=icon}
 "Brawler Whirled"){kind=icon}
 "Frontline Defense Beta 2"){kind=icon}
 "drift"){kind=icon}
 "Noob Defence TD 1.2"){kind=icon}
 "Monster Truck Maniac"){kind=icon}
 "The Necronomicon"){kind=icon}
 "Idle 2.: Konquest"){kind=icon}
 "Vector Runner"){kind=icon}
 "Hexiom Connect"){kind=icon}
 "Epic war"){kind=icon}
 "Protector: Reclaiming the Throne"){kind=icon}
 "Music Catch"){kind=icon}
 "Castle Crashing \"The Beard\""){kind=icon}
 "Super Crazy Guitar Maniac Deluxe 3"){kind=icon}