WaAn, thanks for the info! I'll search for it and see if that's the game I was talking about. :D

Edit:
I found some information on it and some screenshots. The game looks too "modern" to be the classic 2D side-scrolling game I remember. Also, if this helps further, in the first level, the direction of the screen (directing of the scrolling, or whatever) is to the left (instead of to the right = Mario).. And the boy's standing at the top of an inclined plane, then you guide him down, and then he meets his first obstacle: a snail's green slime tracks (and the snail moves away). That's all I remember. :crazy:

Well, it could almost be Keen 4.

Or Cyril Cyberpunk.