What's the fastest way to highlight all possible movement tiles for a player on a square grid? Players can only move up, down, left, right. Tiles can cost more than one movement, multiple levels are available to move, and players can be larger than one tile. Think of games like Fire Emblem, Front Mission, and XCOM.
My first thought was to recursively search for connecting tiles. This quickly demonstrated many shortcomings when blockers, movement costs, and other features were added into the mix.
My second thought was to use an A* pathfinding algorithm to check all tiles presumed valid. Presumed valid tiles would come from an algorithm that generates a diamond of tiles from the player's speed (see example here http://jsfiddle.net/truefreestyle/Suww8/9/). Problem is this seems a little slow and expensive. Is there a faster way?
Edit: In Lua for Corona SDK, I integrated the following movement generation controller. I've linked to a Gist here because the solution is around 90 lines of code.