Are there any useful beat'em tutorials with some AI tips?

I've managed to do a really "meh" but working enemy knockback to my game:
Attachment 20549 Attachment 20551

Here's a GIF how it works in action: http://g.recordit.co/JFCmD1lw6x.gif

However, with this I just can't get to work an AI that follows the player and attacks him if it's close.
I've tried a simple method but it is really basic, not even working with a condition that If the Enemy gets closer than 35 pixels to the Player, his animation changes to Attack:
Attachment 20550

I don't even have an idea how I'm supposed to do this, all I've done before was puzzle games with matrixes and stuff like that we've also learnt at school.

I would appreciate some tips or .MFA files with basic AI that would work with my game after some fine tuning.

Sorry if it's too much to ask or the question's vague.

Thanks!

A really simple way to do this which would require only a few events. If you set the enemy's movement (or secondary movement) to bouncing ball then have it look in the direction of the player and start. Another simple method for hit triggering you could have an invisible active object which is a few pixels high and as many wide as you would like the hit triggering to occur that is set to the enemy position and when overlapping the player attack the player. You would need to set an id to the active of the enemy and have it match the id of the invisible active and then on an event where these 2 match set the position of the invisible active to the enemy.

The benefit of using an active is that you can change the shape of the active and have the hit triggering perform differently based on the enemy by having a different mask in a different frame of the animation. So no complex math required if you wanted it to change based on events such as if player is jumping attack.