Really neat! Some feedback: it seems Zenta looks at $TERM to determine whether or not to use "simple" mode, and it seems it might be overly conservative.
I'm a tmux user, and in tmux, $TERM must be "screen-256color" or "tmux-256color". With $TERM set to either of those, zenta uses simple mode.
I can get it to use "full" mode by running it as "TERM=xterm-256color zenta" within tmux and it works fine, but this shouldn't be necessary - I haven't run into any other TUI apps that don't work properly in tmux.
Edit: I just noticed in the README that it seems to be intentional that it uses simple mode in tmux, but I'm not sure why that should be the case, since it clearly works fine. Maybe you could use simple mode for $TERM=screen and normal mode for $TERM=tmux?
On a different note, it seems like it would be more immersive if it took over the entire terminal window while running. Maybe you've already considered that and decided not to.
Anyway, thanks again! I love this.