Can it be played single-player?

[Skyelander]

See title.

[themilkman]

You mean practice? Yep.

[Andbrew]

Yes, although don't expect much from it.

[Engicop]

Yes, but remember to bring TNTs in your inventory and suicide everytime you run out of ammo.

[Ëvïlnïck8 ゴゴゴ]

Yes, you can play the online modes with bots and the bots are decent i geuss,

But since it are bots after 10 hours or so you seen basicly what the bots have to offer.
Whatever you think that is accapteble depens on you.

[Watercrown123]

There are bots, but do not buy the game just to play with them, it's definitely not made for that. The bots are more for practice before getting into proper MP matches, and that's definitely the main purpose of the game.

[Guns4Hire]

Originally posted by TheEngiGuy:

Yes, but remember to bring TNTs in your inventory and suicide everytime you run out of ammo.

you don't need to kill yourself for ammo. You could play as an officer and request for supply drop.