The mod offers three single-player maps, both with an easy mode for those who don't want to deal with frustration, and a hard mode claiming to be for those looking for a true challenge.
From the description:
Das Roboss is a 3 map series of single player goodness for Half-Life 2. I made a number of HL1 single player maps and I've been itching to make a good HL2 set. DR is difficult. After my last release "Infinite Rift" I got a lot of feedback saying it was too easy. I didn't want to make that mistake again. If you don't want to be frustrated you will probably like Easy mode. If you want a real challenge try out Hard.