20 - nerd safe house

This zombie apocalypse is a tough thing. Dozens of zombies are following you and looking forward to have a nice snack, when some fat guy appears. You outrun him easily, so eating all of him will keep the zombies busy - for a while. So after you keep running a few blocks, you find a safe house. As you stand there panting, sweating and sighing at their door you notice: "Hey, I probably sound just like a zombie." And this is where the automatic defense system kicks in. A big, laser-zoom explosion-looming automatic spring gun locks in on you. Nice. That's what you get for leaving a fat person behind. All your yelling "Help, help. I'm human and... and I have weapons" (a lie), remains unheard. When finally somebody responds on the intercom: "Oh are you? This safe house is for nerds only! Show us how smart you are and find the missing token." So there you go. Try solving the annoying puzzle at nerd safe house or zombies will eat your soul!
 

credits: 100 +3 (1st), +2 (2nd), +1 (3rd)