I never had a game that literally told me I have to play 10 hours for the hard badge.
@DonRosenberger
Spider Legs are not enough, you also need a lot of firepower for the boss.
Replay the level aver you have better weapons.
The best weapon against ninjas are burning temples. They do area damage and will hit invisible ninjas, they need to be triggered by another enemy though. At full level, they will even slow down ninjas.
Place two at the entrance and make sure they are the first to hit opponents.
All you need is a single Heavy Cannon, because it does insane damage at high levels.
It is hard to hit at the beginning, but once you mastered it, you can kill everything with a single hit.
Is it normal that my opponent has negative quantum?
I destroyed his time factory, but he is still able to play time cards and gets negative time quantum.
Also monsters I killed with pandemonium suddently come back.
The game does this since the update.