There's also a fair amount of technical improvement. The visual boost is obvious – though the game is gorgeous because of the art direction rather than raw engine power - but there's also a vastly improved AI that no longer struggles with vitally important things like basic pathfinding. Thankfully the 12-unit selection limit is also gone, which makes squad micromanagement substantially easier. StarCraft is hard enough as it is, after all.
The campaign is full of neat tricks, and it never repeats them. One level has you racing against a mercenary captain to harvest minerals; another has you blowing up targets before a powerful enemy character gets to them. Elsewhere there's one where you're providing fire support to an NPC while he runs around, guns blazing, and takes sips from his hipflask. There's even a bit where Blizzard takes cues from the 2D platformer genre, having you zoom from left to right to avoid an unstoppable wall of fire. The basics - building a base, some bunkers, a few marines and a couple of medics - are always in place, but Blizzard insists on throwing a unique element into each stage to both keep you on your toes and stop the hefty campaign from descending into tedious cycles.
StarCraft II's stages sprawl across the galaxy, taking you through a variety of planets and palettes: across ornate temples, dingy caverns, charred and ashen wastelands and factories with spinning conveyor belts and red-hot smelting pools. These worlds boast intricate design and an abundance of incidental details, each with a unique aesthetic stamp, with textures and models rarely carrying over from one level to the next.
You won't see all of them in a single run of the campaign, though, as StarCraft II occasionally commits to branching paths and forces you to ally yourself with a particular character (and their subsequent level) at the expense of another. These choices are few and far between, and while each one is quite exciting they mostly have negligible impact on the campaign's direction. You might find yourself being forced to choose between the ability to manufacture Spectre or Ghost units, for instance, but at the end of the day it's like comparing two varieties of apple instead of something more significant, like oranges and pears.
Unit and base upgrades are far more significant. Money is awarded for completing missions and goes on buffing the stats of your units, each of which get two potential upgrades - Siege Tanks the option to do 75 per cent less damage to friendly units, for example. Research points, gained from accomplishing bonus objectives in levels, come in two varieties, Protoss and Zerg, and you can choose one of two upgrades every time you accrue five points in each. By the time the end credits scroll you might have the ability to call down supply depots and units from space, manufacture pop-up flame towers and even control the minds of Zerg units. You'll also be able to construct Vultures, Wraiths, Firebats and Goliaths - powerful returning units from the original that don't show up in multiplayer.
The campaign is deftly executed, and Blizzard has successfully managed to shoehorn an overarching narrative and solid characters into a genre naturally opposed to such nuance. A sharp mind is required to clear the campaign, but lightning-fast micromanagement skills are not: StarCraft II manages to remain a challenging game without falling into that trap, which made the closing levels of the original more annoying than gratifying.
One potential problem is that the single-player campaign, with all its buffs, upgrades and exclusive units, makes an incredibly poor way to introduce you to the multiplayer part of the game. However, Blizzard nips this issue in the bud with a series of challenge missions: nine detailed, lavish arenas with limited units, pre-selected groups of enemies and a rigorous marking criteria, with a countdown timer and flashing on-screen commands segueing you from one demanding skirmish to the next. Each arena revolves around a certain theme - perfecting your build order, learning how to counter certain units - that should lend a helping hand, or at least provide a bit of practice, for the kind of tricks you'll need to last longer than five minutes in competitive multiplayer.