Nucleus embodies everything that is King of the Hill - a central slaughter zone built entirely of explosions with just enough complexity around the edges to make tactics possible. The new mode is more than just maps: even the oldest player gets that great “new game” rush as they work out how classes contribute to victory.

We’ll fight to the death for whatever this thing is!
1. Scout
Make no mistake: this update is an apology to Scouts, a gushing love letter which says “We’re really sorry about your uselessness on Dustbowl and every payload map!” The Scout’s double capture speed has never been more useful, trading maneuverability to tick down the clock so even when you die you’ve helped your team win.
The confined capture point and linear walkways make the newly-useful Sandman a perfect weapon. A Scout without a double-jump simply wasn’t a scout, he was a piece of tissue paper that fell onto the playfield. Now he’s got his bounce back and it only cost him a quarter of his health - and if you actually needed the extra 30 health you weren’t playing Scout right to begin with.
2,4 Soldier, Demo
If you can’t work out how a centralized capture point is perfect explosive ordnance-wielders, you might want to choose a more suitable game. Like knitting. As well as the excellent “clear the point” barrages, you can blow people off the narrow nucleus walkways and the vertical nature of the map means rocket-jumping is a whole new artform.
Rocketjump onto the sloped roofs to rain down explosive death.
3. Pyro
An interesting combination: flamethrowers are beyond perfect for crowed points, but actually getting there over the incredibly exposed walkway is suicide. Go in with a group, airblast opponents off the walkways, and remember your real job: spychecking. The circular tracks around the arena mean those backstabbers have never been closer to your spawn, and a burning spy is still the most beautiful sight in the game.
5. Heavy
The Scout’s gain is the Heavy’s loss: still great for dominating the point, but you need a medic and you need to be good. Nucleus is a total sniper-fest so you need to duck and weave with near-psychic abilities for every inch of advance. Learn
the art of sniper-bobbing and don’t ever stand when on the point: those bits of cover are in there for a reason!
6. Engineer
A tricky but extremely fun adaptation. Nucleus simply isn’t big enough to make teleportation the game-winner it was before (even Viaduct has great tele-spots), switching your role to area control or harassment. The former requires teamwork - choose a region (either the upper decks or the lower opposite basement) and build up, bringing sentries and dispensers to let your team advance with impunity. Throw up a teleporter if you like, but don’t expect it to last long - your spawn is simply too vulnerable (which is why some engies choose to protect the spawn exit with their hardware).
Don’t worry if you can’t see the walkway - your gun can!
The other option is harassment. Resist the urge to try to cover the point itself, as you and everything you create will be blown to bits, but shuttle around erecting sentries wherever they’ll give enemies a nasty surprise. Under the stairwells is an excellent location, covering regions of walkways and the lower ring, and every time it gets blown up (usually after only a few kills) erect it somewhere else. Keep moving, keep slowing them down, and only go engy at all if you’ve at least 8 people on the team.
7. Sniper
If you need the sniper-perfection of nucleus explained: don’t play sniper. In fact, “don’t play sniper” is still the difficult sniper skill on any
TF2 server, with some public games featuring five or six the Ozzie marksmen. These teams
always lose. Two snipers is plenty, and watch your back: the extremely cramped quarters mean spies, scouts and pyros are only ever seconds away.
Nucleus Snipers see this a lot
PS: The way the glass wall in front of the spawn shows who’s about to be snipable is glorious.
8. Medic
The medic’s effects seem undone on these small maps - people don’t see the point in keeping you alive when the spawn is so close. And when people don’t see the benefit in “reversing damage” and “UBER INVINCIBILITY”, something is wrong. The old rule of “Most medics wins” is still true, you just have to work harder to stay alive - and hope you have a team smart enough to help you.
9. Spy
Nucleus is a real reward of skill for a single spy, and an absolute deathzone for more than that. Central fighting is so intense that you can’t spare more than one player for espionage, but that spy benefits from the small map. No more hiding and sprinting for two miles to get one kill, here you can go on a backstabbing rampage around their spawn or sniper deck in moments. The one way spawn exits (most people go along the level way instead of taking the stairs) mean an accurate spy can take out two or three spines per pass, before clearing up to the sniper deck and punishing the long range killers.