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Useless

Devoid of anything more than a small (and very basic) code snippet, this "tutorial" is pretty useless. Spiff it up with methods of how to change the speed using variables, add things like acceleration, friction, gravity and so forth, and you'll have something that can be of use to people.

Furthermore: When writing a tutorial, make sure not to make it simply a source for a quick copy-paste job. Writing up the code in small, well-explained portions (with a small exercise in the end, perhaps) is best.

I gave this a zero, because in my opinion, it's useless. That code you provided can be easily found in tutorials on other websites, on the BBS, and through a small bit of studying. Try again with a more complete and comprehensive tutorial.

Rushed

As you said yourself, this was done overnight. It's clearly rushed, and needs polish. If you need to make excuses in the "Author Comments" field, you probably shouldn't post it.
Work on this more and it could be decent.

Poor

Very poor, in my opinion. Could use a lot of work.
The gameplay was monotonous and unoriginal. The graphics look rushed. It looks as if no effort was put into them, at all. The gun, when equipped, doesn't tilt along with the car, for example.

I recommend polishing this up a lot, adding more diversity into the gameplay, fixing bugs and putting more time into the visuals. Until then, it's not something I'd want to spend my time playing.