I'm making a game that would best be described as a side scroller. I'm in the planning stage of this game and I'm looking for some ideas.

I have three main elements so far...
The player:
- Moves around the level, jump up, drop down, move left and move right.
- Attacks enemies adjacent (left or right)

The Enemies:
(Many different types but all have these fundimentals)
- Moves in any combo of these: left, right, jump up, jump down.
- Some may attack with bullets (or fire, havn't decided )

The Level:
- any given square can allows the player (and enemies) to move freely through left and right, it can be stood on top of and wolked through (left and right). If the player/enemy is below it they can jump up through them and land ontop of or inside one... I hope this describes them well enough.
- some squares can not be jumped or moved through, only walked on top of.

Thats about it for the description, any unclearities ask.

Now if you're still reading heres my question:
I'm looking for a good way to know where the player/enemy can or cannot go. Im thinking that I assume the current position is a valid place for it to be, then move it with its x speed and y speed to get a new position and it thats not the same square then check to see if they can and if not then revert to the old position??? Sound good you guys?

It sounds good to me, but if you can think of anything I can't or forsee some problem I'd really appreciate the insight.

Thanks (just for reading this),

NOMAD