I am trying to make a jumper game like doodle jump and I want to create a platform that kills you when you jump on it, the problem is that I don't know how to let the main character pass through the platform, it dies when it touch from the bottom
I have not played doodle jump but still I think I understood what you want , try changing the collision shape of the platform and play around with it , I am 99% sure you will be able to achieve what you want by it. if your platform is rectangle set a rectangular collision shape that is only covering the bottom part where you want the character to do and the rest is not included in the collision shape.
No, I need that the character can pass through the platform once (From the bottom) and if it touches the same platform again it dies