The Cruel Dozen is a map for time-trial enthusiasts who are looking for a tough challenge. It consists of twelve rooms, most of which involve one single impulse-combo-jump.
Warning:

Casual time-trial players may suffer from head-bang-on-keyboard syndrome. Consider to practice advanced moves before playing this map.
Considering the variety of required movement techniques and the precise timing needed for some challenges, this is technically the hardest map I have seen so far. With technically I refer to the fact that there are no pushers, triggers, visual distractions or passages without checkpoints that may feel random or unfair. If you get stuck, have a look at the demo.
NOTE: This map is a remix and expansion of HardCore, which was originally created by [RM]Temka and later remade, polished up and enlarged by TristamK. I would like to put TristamK as the first author here, given that he agrees with the changes and additions i made. I am open to suggestions for another map title. For details, see the file cruelDozen.txt.