i wouldnt spawn and destroy it, i would do it like this:
have the platform wherever you want it. Now say you want it to disapear after ten seconds, then apear again another ten seconds after that.
Have a timer in the platform every 10 seconds change attribute self color alpha to 0
then make a rule when attrbute self colo alpha=0 then put a timer in that rule after 10 seconds run to completion checked change attreibute self color alpha to 1
then whatever you want to collide with the platofrm, have the collide behavior for thos objects in the platform and in a rule when attribute self color alpha=1 so they only collide when its visible
Comments
have the platform wherever you want it. Now say you want it to disapear after ten seconds, then apear again another ten seconds after that.
Have a timer in the platform every 10 seconds change attribute self color alpha to 0
then make a rule when attrbute self colo alpha=0
then put a timer in that rule after 10 seconds run to completion checked
change attreibute self color alpha to 1
then whatever you want to collide with the platofrm, have the collide behavior for thos objects in the platform and in a rule when attribute self color alpha=1 so they only collide when its visible
cheers