Here's what you see when you first open the editor:


The editor itself is pretty straight forward. Each tile can only be of one type. Each type has some basic rules for placement and when you place a tile illegally it highlights red and tells you where you went wrong. I'll leave the map-making up to you, lets just have a look at the different options in the top right of screen...

Reset Options - resets the options, obviously.

Infestation - sets how much of the map is covered in alien growth, the infestation produces fog on the ground and grows up the walls, often obscuring buttons. If there is Infestation of any kind the aliens tend to hide in to ambush you rather than hunt you down; so if you are building a map where you want the beasties to rush you, set it to none.
- none - disables it
- less - less than half of the map covered
- more - more than half of the map covered
- total - every tile has infestation growth

Power - sets if the level starts with the power either on or off. When the power is off you have to bump into doors to force them open and you will need to find a Breaker to turn the power on in order to activate sentries, fences, databanks, etc. Breakers also refill your flashlight battery while you are near them.

Breaches - sets the rules for where breaches can open. Breaches are where the aliens spawn from.
- normal - breaches only occur in dead ends (marked by the purple square in the editor)
- random - breaches can occur in any location on the map, not just dead ends.

Astro-Creeps - sets if those little flying bastards can spawn or not. If set to off only the large xenomorphs will spawn.

Difficulty - sets the time between new breaches opening as well as the time between aliens spawning. Easier settings have long intervals (ie: breaches every 10 - 60 secs & spawns every 10 - 20 secs), harder settings have shorter intervals (ie: breaches every 1 - 2 secs & spawns every 3 - 5 secs).
- random all - sets the time intervals to their widest interval settings (1 - 60 secs)
- random each - randomly picks a setting from one of the other difficulties each time the map is started

Power Failure - sets if power failure can happen and what triggers it
- none - no chance of power failing
- 1/8, 1/16 or 1/32 - power has a chance to fail only when interacting with doors, fences, databanks, sentries, coolant, etc. The power has no chance to fail if you are not interacting with an object. The higher the second number the lower the effective chance of power failure.
- 30-60, 60-120 or 120-240 - power has a 50% chance to fail once during the set time interval. The higher the numbers the lower the effective chance of power failure.

Style - the texture set used. Each one explained below...