Hot Spot markers for Alien Ambush scenarios

For future games where brave marines will be attacked by an endless horde of alien monsters, I needed hotspots for the Ambush Alley rules and my lovely fiancee kept in mind, that everything can be used to build terrain (true love...). Therefore she brought me this:

Out of the lit or top I created this (using the wiremash one fellow gamer gave me as a gift):

 Each shaft or tunnel entrance represents one hot spot and until the marines seal them or blow them, endless hordes will emerge. Imagine a whole abandoned tunnel network down there crawling with aliens...

The poor guy on guard doesn't have a clue, what is in store for him....

This, now disappeared guard doesn't have to worry anymore....