Reaction fire triggers

Certain actions will trigger reaction fire from aliens; others will not, even though they may reduce your TUs. (However, if you have used up several TUs doing "safe" actions then conclude with a reaction-triggering one, an alien with sufficient TUs will make several "stored up" reaction shots against you.)

The following is a (possibly incomplete) list of which actions will and will not trigger reaction fire. Opposing units also need to be facing your unit(s) and have sufficient TUs available; see Reaction fire formula for more details.

Will trigger reaction shots from an alien facing you:

• Firing any weapon
• Kneeling or standing
• Any walking/flying movement
• Using a lift
• Throwing any object

Will trigger reaction shots from an alien not facing you:

• Hitting an alien (they will spin around and return fire) (does not include Stun Rods)

Will never trigger reaction shots:

• Turning in place
• Firing a weapon from beyond the alien's visual range
• Taking any action (including firing a weapon) from a position hidden to the alien
• Priming a grenade
• Firing at (but missing) an alien not facing you
• Any action on the inventory screen (moving, dropping or picking up objects; loading or unloading a weapon)
• Using a Medi-Kit, Mind Probe or Motion Scanner
• Using a Stun Rod (walking toward the alien is what gets you killed!)
• Being the first unit to enter an alien's line of sight. This means you can safely walk through a door, even with no TUs left! It's your next action that will get you killed. (Subsequent units which enter the door will also get shot at -- the alien is no longer "surprised".)

Currently unknown/untested:

• Hitting an alien not facing you with indirect fire from HE, IC, or stun rounds