fix test_platformer.py on slow hardware like raspi3 (player was falli…

…ng bellow floor)

test/test_platformer.py

@@ -29,6 +29,11 @@ def start(self):
 
     def step(self, dt):
         global keyboard, scroller
+        if dt > 0.1:
+            # a too big dt will move the player through walls
+            # dt can be big at startup in slow hardware, as a raspi3
+            # so do nothing on big dt
+            return
         vx, vy = self.target.velocity
 
         # using the player controls, gravity and other acceleration influences