I'm not sure if this is the proper forum for asking this but it's as good as any to start. I'm designing a 2D maze game in which I'll be including a number of power ups, power downs and obstacles. The question is, how does one design in when and where power ups et al need to appear? From experience the distribution of power up on a variety of games I've played seems to be all over the place. Occasionally at first, moderately in the middle. And towards the upper rounds they can almost non-existent to smothering. Sometimes they appear to be random while other times they either show up when you need them most or when they aren't much help. Is there any approach I should take to this part of my design? Thanks, Lilith

Usually, this is called Level Design. As the designer, you decide what type of experience you want your user to have... there's no "ways" of placing power ups, you just place them to help the user get through the level... not sure I'm helping though...

xEricx is right, it's a level-design issue. Having that said, there are a few 'rules', or common situations, you can go for.

For example, you can use powerups to create a flow around the level. Place an assault rifle upstairs, and some grenades for it's attached grenade launcher down below, and most players won't stay up there even though it given them a height advantage. You can almost enforce flow with powerups, or give subtle nudges.
You can also provide interesting choices to players. When a strong powerup is placed in an open and vulnerable place, it may tempt daring players to grab it, or instead to stay waiting to hit someone else who tries.

Of course, the kind of situations you can create depends on the game type, and setting up traps isn´t really possible for a 2D game that shows the complete playfield at once, but I hope this gives you some ideas. Providing less powerups later in the game is simply a choice. Whatever you do, be sure to playtest it before calling it final. Good luck. :)