Button
Brick Name = "button"
[Delay=0] onActivate -> <NAMED BRICK: bridge> -> setRendering -> [ticked]
[Delay=0] onActivate -> <NAMED BRICK: bridge> -> setColliding -> [ticked]
[Delay=0] onActivate -> <NAMED BRICK: bridge> -> setRaycasting -> [ticked]
[Delay=3000] onActivate -> <NAMED BRICK: bridge> -> setRendering -> [unticked]
[Delay=3000] onActivate -> <NAMED BRICK: bridge> -> setColliding -> [unticked]
[Delay=3000] onActivate -> <NAMED BRICK: bridge> -> setRaycasting -> [unticked]
[Delay=0] onActivate -> Self -> cancelEvents
Each Brick in the Bridge/Platform
Brick Name = "bridge"
This should let you click the button, make the "bridge" appear for three seconds, then make it disappear. If you click the button at any time while you're on the bridge, it'll stay for three seconds after that. (You might want some things with setEventEnabled to stop this)