Space Hulk: Tactics

Pretty straightforward achievement.

First off, from the main menu, select "Mission Editor", then "Create".

From there, phase 1 "tiles" is to build the map using the 2d shapes, RB/LB to change type, LT/RT to change different piece, D-pad to rotate, and A to place. When you are happy with your map (make sure you leave to some open bits for Genestealers to come from), push Y to move to phase 2, "interactive objects" such as doors, marine/genestealer entry points.

Use back to give your map a name, and RT to give it an objective. Survive is probably the easiest, as it does not involve any more moving parts, such as exit, and just needs entry points for Marines and genestealers.

If it doesn't let you publish, check by pushing start that there are no red x's which will prevent you (eg no objective chosen/no spawn points, etc).

KEY to getting this achievement is that there are also no yellow cautionary comments there as well, such as "corridor of 12 squares without a door", as this will still let you publish, but wont unlock the achievement .

When you are happy, push start, and select "publish". Achievement unlocked!

In addition, you should also unlock

Good luck!!