As far as i know memory pooling is a good choice if youre creating and deleting objects during the gameplay, outside the load/initialize part of your game. Allocating/deallocating memory is a expensive operation, thats why object pooling is good. You can reuse the memory previously allocated by anot...

For the same input, and same binary, Box2D will reproduce any simulation

That means i will get the same result as long as i run the game and the replay on the same platform, right?

The docs says about the floating point problem but only when you mix platforms, like windows and unix

I'm developing a game and i want to store the keys pressed by the player to use later on some replay system and validation.

Is passing a fixed dt to world:update enough?

1) you can use https://www.mapeditor.org/, it has a geometry editor with rectangles, circles and polygons. You can also natively export the map to a .lua file.

Since rectangles are made of lines you could check line to line collision, something like https://github.com/processing/processin ... -Detection. If any line of Rectangle A intersects any line of Rectangle B then there are colliding.