Not bad, definitely feels very unfinished however. I found the mouse sensitivity a little high, would have liked keys to turn as well as strafe as an alternative to steering with the mouse, and a mouse sensitivity setting, and I'd consider a third person view as an option.
The only really obvious 'criticisms' are more a case of 'you probably just haven't done that yet'- environment is very plain, flat, and square, could do with more landscape variety & size, obstacles, powerups, traps, shelters, levels with increasing difficulty. Could do with a blood curdling scream as you're abducted though
Your core mechanic is obviously a 'last man standing' scenario, and secondary mechanic is 'get the other guys caught first'. That's just begging for a multiplayer mode, although it'll need a much more interesting environment to make that worthwhile.
Possible power-up suggestions:
* One-shot tractor beam disabler- but if you use it too late, you fall to your death
* Grappling hook/lasso- grab a tree on the way up to save yourself
* Decoy- throws the beam off the scent briefly
* Speed boost
Possibly additional alien abilities:
* Melt/shatter obstacles to get to you
* Pick up rocks or other debris and drop it to break up obstacles
* Split beam
* Reflecting beam that can pull you out from under an obstacle
