Followup to Frank's post - find a pair of red/blue 3D glasses, or look at the image through a red filter to see the message clearly.

I clued the achievements together and played around with some RGB values and got this:

https://steamuserimages-a.akamaihd.net/ugc/442827467488748615/3915AF74CF494C10EC6E7CD3CC5C1B43F3270DA6/

I've got it. In-game, it adds jump height x2, speed x2, and makes the player's eye level and hitbox really tiny. It might do more, going to play around with it for a bit.

edit: the effects stack. keep pasting the cheat into the console and you continuously gain jump height and speed. You don't get any smaller after the first input though.

Finally someone who doesn't just dance around the fucking achievement like it's some kind of puzzle.

Wow bad lumpak

Both ~ (aka `) and tab work for me (US keyboard). That's probably done so anyone can enter the console without issue, regardless of the keyboard layout.

I'd also like to know how you autocomplete in this console, since tab just closes it again.

how do you get that autocomplete thing to show up? Where you type in letters and it shows possible matches? I've just been typing random crap is the console (with little sucess, as you can imagine)

It was a localisation issue, on a Uk keyboard it#s not ~ but Tab.

You probably didn't enable the console. Remember you have to be in-game before you press ~.