I got the same problem with the gunmen not shooting at wave 17 when there were 50 of them. Could it be because of Chrome? It sucks because there are no save files.
I have done the hard badge in like 30 minutes or less. It's like playing on an ice level, but worse. It feels like keeping the guy standing up helps with dodging and shooting. The hearts just drop through the earth, which sucks as you want to as many lives as possible.
For the first boss level, use bombers and support fire against the big balloons and don't take damage so that when the boss reaches you, you can survive it once and have enough time to kill it. I'm not sure if the that one point in building armor affects it or not.
Tips:
Upgrade Winged bombers. Faster bombers mean quicker death to big balloons.
At the very beginning, use the points for shell damage. Upgrade the main flak cannon and winged bombers. Once, you feel comfortable, start getting the building stuff.
Use the special airstrikes when you are low on ammo or overwhelmed with balloons.
For me right now on elite, it's more of an endurance game.
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 "Inferno Legend"){kind=icon}
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I like it.Keep on enjoying it.