jojoxpz no you didnt open all chests...you pro'lly missed the one that is barely notable by the area with the 20 medals needed. it has a chest in the top right corner, next to the crab.
btw, i just finished the game with all upgrades and want to say: bug with fourth boss- his hp doesnt appear untill you kill him. not really a problem, i just wanted to report that bug.
my tank was destroyed some time after the first boss's death. i was in the way for the money. then, when i finally repaired, i was 10 inches away from the 3 chests....and they disappeared. MAD MAD MAD!!!! yet the games cool.
my strategy against heros: before they spawn, i get a berserker(or whatever here i have by the time) and some zombies. then i get auto on and they start raising zombies. alot of them
when the hero spawns i select all and aim at the hero
zombie is easily the most usefull minion ever with upgrades, he can be spawned once or twice, i leave to play ffiv and when i come back all the town is destroyed
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