That's a good feedback! I thought the sawblades wouldn't be such a problem as they follow a very specific pattern : They just turn around in their own circle. But since we can't see them, we get no information about the danger.
I think we'll add some kind of rail to tell the player where a sawblade will pass by; I don't know if it will be blue or black though. Making it blue would push the player in a strategy where he would keep the sawblade intact in order to be aware of passing-by robots. Having it black could still feel unfair even if its by a smaller extent.