I have been using keynav (https://github.com/jordansissel/keynav) for convenience for a while now, but still pick the mouse up for selecting text outside of the terminal since dragging is bugged.
This is great.
I have been using something called keynav[1], for getting a similar grid mode. I would never guess how intuitive it is.
It doesn't replace the mouse, but it's helpful for that occasional click in the middle of heavy keyboarding.
I wouldn't game with it, but keynav (https://www.semicomplete.com/projects/keynav/ / https://github.com/jordansissel/keynav) is pretty great.
For linux use: https://github.com/jordansissel/keynav
Please take a look at a program called `keynav`. I use it for clicking things with my keyboard instead of the mouse, and it works almost flawlessly, except in VirtualBox.
It's source-included, so you can figure out the method they use.
Since it wasn't linked last time I looked, code is also at https://github.com/jordansissel/keynav
Shameless plug: I maintain a fork at https://github.com/yjftsjthsd-g/keynav because the original author hasn't been active in a while.
Edit: wrong link :)