For all you cheaters out there, this is a helpful guide that will tell you how to win the game. If you want to just figure it out yourself (which is what I would recommend), please go back now and do not look at the following content.

WARNING: SPOILERS

Run the game.

It will appear with a door with 'Lab 14' on it, press enter.

You will see a sequence saying:

"Welcome to Research Lab 14

Error

System Down"

You will then proceed to the game.

I (no hint):
Walk right to the door.

II (What goes up...):
Walk over the pit and to the door (do not jump).

III (Move the Window):
Drag the game window around the screen (not the window inside the game, the display window).

IV (5 is fake):
Walk up beneath the door, and jump up (notice that the fifth block is fake, and you can jump through it) heading right. Keep heading right till you can't move anymore and you can see your ears in the window. Jump left and exit the door.

V (Turn back now):
Go left, then go out the door.

VI (Backwards thinking):
Walk right and press the <down> key, exit door.

VII (Hint):
Jump on top of the Hint word and jump to the exit door.

VIII (Not what you'd expect):
Move the crate so that the second crate can fall on top of it. Then jump over the spikes and to the second level. Push the crate left and down the gap. Jump down the gap onto the two crates, and jump onto the exit platform.

IX (Fooled you):
On top of the pit, there are a couple places where you will fall in. Find these via trail and error and jump over them. There is also a place on the top level where it places you somewhere else, find this also and jump over it. Go through door.

X (R. Kelly Hit):
By repeatedly pressing the <up> key, you will find that you can fly. Fly to the door and exit.

H (Awareness):
Press <H> (H does not mean 11, nor is it a Roman Numeral at all).

XII (What you'd expect this time):
Jump over the spikes and the crate and over to the platform by the word 'Time.' Keep walking right and you will fall down a pit, containing a door. Go out the door.

XIII (I lied):
Walk right until you fall into spikes. The rest of the level will then appear. Jump onto the one-block platforms and proceed through the door.

XVI (Lose focus):
You can see that there is no exit door in this level, so you need to lose focus. Minimize the window or click outside the window. Proceed through the newly appeared door.

XV (Start ->):
At the bottom of your computer screen on the task bar, you will see it says 'Press T.' Do exactly so.

XVI (Up and over):
Get over to the tower and stand by it. Click and slowly drag yourself to the top of the tower. Jump off and exit through the door.

XVII (Mice know):
At the beginning of the level, your mouse should go to a different position automatically. If you moved the mouse and missed it, kill yourself and it will move there again. Keep the mouse in it's location, and jump up to the fourth tower. Jump off onto where the mouse is, jump to the exit platform, and proceed through.

XVIII (Think small):
Minimize the window, then jump on the platforms and over to the door.

XIX (no hint):
You will come in and you will see another character in some floating ship thing. He says that the whole lab is actually an insane asylum and that you will never beat him. He drones on about how he is impossible to beat then starts shooting red triangles everywhere, still talking about how he is invincible. He actually is invincible, so escape. Escape by pressing <Esc>.

You will see a congratulations screen saying you survived Lab 14. It will then take you back to the menu.

Also, if you're still confused about it, you can look at EGalway's gameplay video where he played it from start to finish. It is here.