Congrats on your responsive tool. I've spent some time with it since purchase. Some thoughts Ignore at will!

1) previously mentioned the black/gray interface is hard to read, and an option to change that would be great.
2) I am not a newbie for responsive and have been doing this way for some time, but I haven't every deployed the "grid" method, so this was fun to learn. So to figure out how to use your new tool, I started with some basics, exported and examined the results. I learn better by doing than by reading directions. So to that end, I suggest some really simple starters with no frills, etc to learn from. And if that is helpful, do you want members to send in their starters? It might be a nice collection if folks keep them drop dead simple for learning such as your simple "push" concept.
3) Default css that includes coffee grinder, coffee etc is distracting. When I exported my testing, I renamed, etc. Maybe there is a way to export with other set defaults?
4) If not read carefully, the product description could easily be misinterpreted as a web design tool. I know you say it isn't, but it didn't dawn on me until after purchase what it really was. Not disappointed at all but was surprised.
5) Small typo on some of your tuts. Who's means who is. Whose is the word that is a reference. Sorry, I read so many pages today, I don't recall exactly where I spotted it. :-)

Anyway, I've had fun with it. Still trying to merge into my own work flow, but I can see efficiency value here. Thanks!

#1 You can change the background color of the grid to what ever you want. Select the grid then the Properties tab. Now at the bottom select your favorite color.

No, not the grid. The user interface that serves the app.
:-)

image attached

The right hand panel?

sorry not sure it attached… trying again

yes, right hand panel. Old eyes etc. :-) Just hard to read. I am working on a 32 inch monitor so it's not a space issue, it's a color combination issue.

Ok that would be cool to be able to tweak that for various lighting conditions.

The colors of the interface itself cannot be adjusted. Sorry..