Achron was, to put it bluntly, a very dull and uninteresting rts. But it implemented time travel like no other ever
You had a line of time of your match you could freely jump back into and you could use chronoenergy to give units orders in the past, so that you could for example undo a failed attack, or intercept a flanking action you originally missed.
But it gets weirder: your changes in the past of course alter the history, and so do enemy actions in the past. Changes propagate at a finite speed, so time paradox becomes oscillating changes in the present. You could use this to split the timeline and fight two different games - like build factory A and 20 units. Jump in the past five minutes and use the first unit to kill factory A, and the timeline will keep oscillating between one version where you got your 20 units and a version where you couldn't build them as you had no factory. Build factory B in this version and 20 different units, and now you can play two battles within the same map with the outcomes in the present oscillating as time waves can't converge the paradox
But it gets weirder: late game building allow to teleport unit in the past. You could send five unit from the present in the past to join an attack in the past, and control them in the past. You could send them twenty units from the B timeline into the A timeline, win there, then move them all back in the B timeline. Or you could send five unit in the past, keep them safe until the present, send them in the past again, and again, and again, and then attach with 20 units that are actually the same five unit at different looking in their timeline but all present in the same present. And depending on which one the event kills, future version sent into the past would disappear and their action/damage reversed
But it gets weirder: you can be defeated at any point in take and it doesn't matter as long as one time waves where your chronoenergy generating structures lives. So you need to kill your opponent across all timeline and exhaust their time energy, which means having to enter your enemy paradoxes if they did some
To bad the unit design and the rts mechanic in general where terrible. I wish their engine could be used with some better factions, it would have been a great mechanic to couple with red alert units