I'm sorry but I don't speak English very well, I 'll try to explain my problem.
I'm doing a flappy bird game. I try to make my bird fly (go up), but when I press the spacebar, he goes up, but the more he goes down the more it's difficult to go up.
When I begin, the bird is in the middle of the windows and when I press the spacebar, he goes up. But when he goes down, it's more and more difficult to make him go up.
The behavior is platform, the gravity is 500 and the event is "when the spacebar is pressed, set platform vector y to bird.y -700".
I don't know what's wrong because I follow the step in the tutorials.
Could you help me?