I thought that the best way to teach the player the mechanics/controls is simply by throwing them into the first level, so that they can instantly understand the mechanics. "Learning by dying" :D
Also, i created game levels for the first time, so i thought about making them as difficult as possible, because i also had not that much time than i wanted to waste on making levels...
Spider boy gains kind of momentum when moving or jumping, or what do you exactly mean with momentum?