No problems :)
Groups are a beautiful thing. When you create one, you can make it off by default and activate it through action. So, when I created the group I made sure it was off (rick click > edit > check "active on start").
The group "shoot" is there to make it simple to read and modify. I also added it to give you ideas how to use "groups". The beautiful thing with groups is that it's a very easy way to optimize the program and make it easier to read.
The variable "player" or "enemy" is there for information. You can use it later on to distinguish, let's say how powerful the bullet is depending if you have a powerup. Right now I added it to check if it's a bullet from the player, if it is, the bullet won't hit the player only the enemy.
The number one tip I have is to make construct do all the work. It has a very intelligent picking system when you start asking yourself on every event "Which objects will construct 2 pick when I do this condition?".
If you have anymore questions just ask.