The Thor is a monster. Hundreds of tons of high-density steel, two legs, four arm-mounted particle beams, a further four artillery cannons secreted away within its excessive shoulderpads and a really bad attitude make it the perfect vehicle for blowing through slow-moving enemies. But it's not invincible.
The Viking is a terror. It's a smaller mech unit armed with two giant gatling guns that can cream infantry in just a few moments. And it's oh-so-manoeuvrable. At any moment, it can fold its legs away and take to the sky. It makes the perfect base raider: fly it round forward defences and set it among the workers and drones for massive economic damage. But it, too, is not invincible.
This is the challenge and thrill of Starcraft II, the long, long awaited follow-up to the brilliant sci-fi strategy original. In your hands are tiny soldiers and glorious machinery. When you throw them against an enemy the result is usually swift and obvious: you either win, or you don't.
The weak-points are clear. Groups of Thors waddle into action, their stumpy legs barely carrying the great mass of metal and gunpowder hefted on their iron shoulders. All that weight causes them problems when turning. Like the Death Star, their guns can't track fast-moving targets. The canny commander will get infantry in close to circle the Thor, cackling as they dodge its artillery barrage.
In the same way that dogs can't look up, the Viking can't defend itself from surface attack when on high, or air attack when grounded. Entire platoons can vanish
if caught out.
This is deliberate, purposeful, clever balancing. The Blizzard team making Starcraft II are all long-term veterans of real-time strategy development. They're led by Rob Pardo - he worked as a designer on the original Starcraft, led the development of its expansion pack, Brood War, and now supervises design on all Blizzard's games.
Following him is Dustin Browder - new to Blizzard, but a long-term employee of EA. He's credited as design lead on all of EA's strategy games since Red Alert, including C&C Generals and Battle for Middle-Earth.
It's a fascinating collaboration. Dustin explains how, when he joined the team, Rob laid down firm rules for how the sides would function. The main one: invention requires sacrifice. "The fundamental rule is that for every new unit we create for Starcraft II, we have to lose one from the roster." Lose one?
It sounds like heresy. But each new toy has its own strengths and personality. For every fan favourite lost, like the Firebat, a new contender pops up. Yes, the Firebat was hot stuff: scorching entire legions of Zerg.
But the Reapers are cooler: heavily armoured infantry that can leap across gorges with their jetpacks, dropping timed demolition charges. They zip into position, lob their grenades, and get out before any defenders have a chance to react.
Starcraft II doesn't do flashy. It doesn't have the grand overview camera of Supreme Commander, or the extravagant physical destruction of Company of Heroes.
Its thrill is the pure thrill of pitching these toy soldiers against each other. As I dance Reapers around a Thor, giggling as its artillery rounds are dodged by my nimble little troops, I realise I wouldn't have it any other way.