Ultimately it's an RTS... like Star Craft or Command-n-Conquer, but set in the American Civil War. But it can still be fun, especially if you forgive it's shortcomings, which begins with avoiding them. There are some good beginner's tutorials in the forum/steam community.
Don't expect realismSupply is distributed by a single supply unit per corps. If that SU gets captured, that's it. Your units will have no way of replenishing any supply throughout the battle, unless you have a second corps on the field with a second SU.
There is no such thing as cohesion between sister brigades of a division or corps.
it doesn't matter how deep into the woods you are, you can always be seen.
Each unit has a highlighted circle around it, showing how far they can see, which can be blocked by hills and such. Some units see further than others though. EG a skirmisher sees further than a brigade. But the skirmisher is generally 'shaken-out' of the brigade (you get a 250 man skirmisher unit, and your bde is reduced by the same number).
So, you you have a brigade sitting on a hill, but it can see no enemy units. You press 'T' to shake-out the skirmishers from your brigade (they are literally sitting in the brigade's lap... okay, not literally, but practically) and suddenly you can see the enemy units in the forest across the way.
And although your artillery cannot see the enemy themselves, because your artillery are on the back slope of a hill, since your skirmishers can see the enemy, your artillery can now bombard the enemy units.
Line-of-Sight is not reciprocal. There are kind of outlook points, often on hills, but not always, from which you can see nearly the entire battlefield, or that section anyway. So if you have an artillery near one of these outlooks, they can bombard everything within range, but the targets of your artillery cannot see your bombarding artillery to fire back, although your artillery is in an open field, and the enemy's artillery is in a city.
The AI is very sloppy with the SU's, so generally you can capture at least 1 per battle, sometimes a whole slew of them.
The AI often sends lone brigades to try to capture a VP-Location, because the VP-Location is so far behind the lines, the AI assumes the human player will not think of this and not see them until it's too late. You can figure out what generally happens to these units, without ever having played the game. This is when you realize, you are not playing a CW battlefield simulation, but an RTS
Battle lines do not win the battle, mobile power wins. If you can put a 250 man skirmisher on to the flanks of a 2500 man brigades, you will generally break the brigade, allowing you to continue doing this with ever more units. The AI doesn't do much against this.
I'm not terribly good, but I can almost always win. Others are far better than I. There are YT videos where you can watch how the defender with fewer men sends out a few skirmishers and a middle sized cav and obliterates the entire half of the battlefield with almost only these small mobile units:
https://www.youtube.com/watch?v=ggWoHJ8_GAw . Of course this can be fun

, but it's not historical, nor realistic.