[Nephilim]

One trick you can do with Tiled is to have a tileset that includes a 'blocker' tile. If Tiled supports alpha-channelled tilesets (can't remember off the top of my head), then you can make a 25% red wash or something, and then just draw in a walkability layer with the red tile, which would give you an easy, visual way to define walkability. Your exporter could then look at the value of that layer and if it saw a blocker, multiply the terrain tile by -1.

When I was tinkering with Tiled before, I used a similar trick to define script trigger areas - I simply made a tileset that had numbers on each tile, which I could paint with to make areas that trigger scripts - the map just stores a number in that layer, and I look up the script based on the number in an externally-managed script database.
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