My mate is making a tool for DnD players to quickly visualise scenarios

It's cool, and I feel dickish being like "Someone made a cool thing? Those suckers, we already have cool things", but you could get a lot of the same functionality by building on top of other open-source minimalist diagramming tools, some of which I can see have been mentioned in other comments, and just adding on assets for D&D specific stuff. Like I'm not sure what I could do with this that I can't do with excalidraw.

But in terms of more useful feedback

- The way the canvas expands when a line is close to the edge is very clever. It might be useful if that could be done in real time somehow, so that if you're drawing a long line the canvas can keep up with you

- Some more erase and selection options would be cool, if I have to delete a big structure that I made out of a bunch of tiny line segments I think the only way I can do that is individually clicking them.

- Zoom seems kinda janky for me, that might just be my browser (Desktop Safari). Also if there's a way to pan I couldn't get it to work

Cool. We use https://roll20.net/ for that in our DnD group.

Looks great!

Some criticism: Moving the position of a player icon on the map is non-intuitive.

This is surprisingly usable in the current form. Nice!

Features I would like to see:

1. Select walls and move them

2. Select a set of lines and change the scale

3. A few different line types - adding double, wavy and thick would help a lot

4. Change line color.

5. A "gametime" mode where the drawn lines are temporarily immutable but tokens can be easily moved around. Flipping between the two modes should be a single click.

6. Change background color of grid squares - this gets you forest and river and mountains, or bushes and streams and rocks.

Also a button to quickly show a random example to see what it can do would be nice.