When using edge markers why are they not just constant?

I am almost complete with the second tutorial "How to make a platform game" am hesitant to move on until i figure out this issue.

The snail that is on the platform is moving back and forth. However it hits the edge markers about three times before they decide to just fall over the edge on hitting them the forth time or so.

I have reread the tutorial several times. everything checks out. When i debug the screen i do see they they are pulsing instead of being constant.

Why aren't they just constant. Are the snails colliding with it while it is in the middle of the pulse and they are going through the edge marker?

Anyone know what the problem is?

Thanks

Are you using a dedicated sprite for the snail's collisions? If you're not and using the snail sprite itself - do all the frames have an identical collision box?

I was using what the tutorial suggested which was using the snail itself. Without giving it the same collision created for the player. Should it just have a collision box instead? and is that the best practice regardless if the npc is complicated or not?

Personally I always use an invisible sprite for collisions/movement and pin the graphics to it later - to my knowledge this is best practice.

thanks Mr E Bear i will give that a try!!!

Personally I always use an invisible sprite for collisions/movement and pin the graphics to it later - to my knowledge this is best practice.

Ok so i just recreated a second enemy which a dupe of the original snail. Everything is working great!!!

Collisions works a lot better using the invisible col. Is the way collision is taught in this tutorial for npcs not reliable? or is that just a bug in the system in using the npc as its own collision?