I picked up a load of Space Hulk sets for the board sections alone (four of first edition, both expansions and second edition give you a lot of board tiles!). I prefer playing ASC on Space Hulk corridor sections. I still play occasionally. I spent a while rewriting the rules, adding my own house rules, army lists, etc. I named it ASC2 (or ASCII!).

ASC was more flexible than SH. Each model takes an activation, which could be advance, assault, etc. This gives them a specific number of action points, that can be spent on types of action. For example, an assault action gives the base number of action points +2, but they can only be used to move or close combat. Advance gives the base number of action points, used to move, combat or snap fire. Ready Weapon gives only one action point, and an aimed shot.

Combat works rolling a number of dice (D12!) and adding modifiers, attempting to beat the targets armour (or combat roll).

In addition to the standard board/corridor action, there was an exploration phase, involving turning over cards until an encounter was revealed.