I am looking forward to this next Christopher Nolan movie.
That is, I can imagine time as a single axis so that you could go back and forth. (Ooops, about to be eaten by a ghost, let's rewind.) But I can't imagine what it means to go northwest in time.
Disclaimer: my ideas come before having done my homework on the link above, so I need to read Greg Egan's stuff really. He's such a wonderful person and I need to dedicate more brainpower to his work.
In Pacman terms, I guess you could program it so that going up or down with the second joystick changes the terms of the game slightly. Maybe the maze configuration changes or in one timeline the ghosts bounce off you when you run into them but the walls themselves zap you.
In a more nuanced conception of the timeline axis, I suppose y-points would have to be branched or braided off x-points. Maybe that's where the third dimension comes in.
I'm sure Egan has worked it out with more rigor. I checked out the link for one of his books above but I admit I blanched when I got to the synopsis:
Seth is a surveyor, along with his friend Theo, a leech-like creature running through his skull who tells Seth what lies to his left and right.
I've got enough on my plate at the moment with the dissolution of civil society. I'm not sure I'm ready to entertain leech-like symbionts confronting the disintegration of time itself.
For what it's worth, time is distinguished in physics. It isn't just "another dimension" that "happens" to be used as time, but if you could just twist correctly it would become a spatial dimension. It is truly a "time dimension". The simplest way of looking at it is in the Minkowski metric, where distance is SqRt(x^2 + y^2 + z^2 - t^2), note the minus sign on the "t" which distinguishes it.
If you're really up for a solid math-based mind-screw, Greg Egan worked out the shape of physics in a universe that works on essentially Einsteinian relativity, but with two spatial dimensions and two temporal dimensions: https://www.gregegan.net/DICHRONAUTS/DICHRONAUTS.html It turns out that A: sensible things can be said about this and B: it looks nothing like what I expected two temporal dimensions to look.
(And if that's not enough, he's also got a universe of four spatial dimensions: https://www.gregegan.net/ORTHOGONAL/ORTHOGONAL.html)