Thanks so much! Really glad you liked the design of that third mob.
To answer your question: that beam (which is I think you are talking about the first the Whip weapon) aims directly at your mouse cursor at first. However, once you upgrade to having more than 4 whips at once, it switches over to automatic targeting!
Pretty much everything else is fully auto aimed right out of the box the Plasma Gland auto-tracks in range that can be upgraded, and the Claw automatically scans for mobs within your upgrade range.