(I cross-posted this from StackOverflow as this seems to be a more appropriate forum. I've looked around a little here and I did not find an answer, so I hope this is not a recurring question.)

This is a question dealing with 2D world design.

I am playing around by creating a 2D bird's eye view shooter game, and I am looking to make the game sleek and advanced. I hope to be able to write physics so projectiles have momentum and knock-down properties.

I am immediately running into the problem of world design.

I need a way to have level files that store everything there is about a game. This is easiest by just having a grid of objects. But there are thin-walls and other objects that don't seem to fit into a traditional cell of a grid. I want to be able to fit all these together so I can streamline level design; so I don't have to put in the exact pixel-specific start and end of a wall.

There doesn't seem to be an obvious translation from level file to game without forcing myself into a pacman-life scenario, meaning a scenario where the game feels boxy and discrete. There is a contrast between the smoothly (relatively) moving characters and finite jumps in a grid.

I would appreciate an answer that would describe implementation options or point me to resources that do. I would also appreciate references to sites that teach game design.

The language I am using is Java (although I would love to use C or C++, but I can never find convenient resources in those languages).

Thank you for any answers. Please leave any questions in the space below; I will be able to answer them later tonight (28th Nov).