Just like a good demo can sell a game, a disappointing one can lead to lost sales.

Heavenly Sword has been one of the most anticipated PlayStation 3 games since it was unveiled at E3 2005, so when a demo of it was released Thursday, I, like all PlayStation 3 owners in their right minds, downloaded it as soon as it was made available.

After playing the demo, my interest in Heavenly Sword has dropped.

There is not enough variety to the Heavenly Sword demo. After a long, non-interactive introduction you play a short, God of War-like minigame in which you are given on-screen prompts to press specific buttons at specific times to run and jump across severed ropes to reach a small platform. When you reach the platform, you fight a large number of enemies all at once. When you defeat them all, you play a shorter God of War-like minigame and then fight another large group of enemies in a small area, this time on the ground. When you defeat this second group of enemies, larger, more intimidating-looking characters break down a door, implying that a 3rd battle in a tight area against a large number of enemies is about to begin, but the demo ends there.

The combat system in Heavenly Sword is surprisingly deep, but if fighting large numbers of enemies simultaneously in small arenas is what you do for the vast majority of the full game, as the demo implies, that deep combat is going to get monotonous early.

I have been tracking Heavenly Sword for more than a year, so I know that there will be more to the full game than multi-enemy combat in tight spaces and short, God of War-like minigames (such as boss battles; more stealthy, less action-y sequences and use of cannons), but the demo's almost complete focus on multi-enemy combat has me wondering if there will be enough of the other elements to prevent the game from getting dull.

I still have some interest in Heavenly Sword because of what I know from earlier previews and gameplay videos, but if the demo were my first knowledge of the game, I would ignore all future information about it (the full game), and I certainly would not buy a retail copy.

Indeed. A disappointing demo can lead to lost sales.

Perhaps if the Heavenly Sword demo's 2nd minigame had been followed by something other than a 2nd multi-enemy combat sequence (or 3rd minigame) I would be just as excited (or more) for Heavenly Sword as I was before playing the demo, but as it is, the demo does not leave a positive impression.

Or maybe that not a fight against a large number of enemies in a tight area would have convinced me not to buy the full game. The lack of variety in the demo has me worried that Heavenly Sword's other elements might be broken.

The Heavenly Sword demo is certainly not the first disappointing demo for an anticipated, upcoming game, and a disappointing demo does not necessarily mean that the full game will also disappoint, but the first direct impression is the most important--if I hadn't been so hyped for Shadow of the Colossus by the time I played its too short and too easy demo I would not have purchased the full game--and with digital distribution now a viable option for game demos, demos have the potential to be the greatest influence on game sales--more than professional reviews or word-of-mouth.

A game demo should not focus on a single element of the full game. It might be the best element, but giving players the impression that that is what they will be doing for the vast majority of 20+ hours turns them off. Too much of a good thing is not a good thing. We need variety to stay interested for more than a few minutes at a time.

For example, the Ninja Gaiden Sigma demo sold me Ninja Gaiden Sigma. I was ignoring this game prior to the demo, passing it off as a rehash of an Xbox game (and it is, but it has aged better than expected). Fighting large numbers of enemies in tight areas is a part of the demo, but it does not dominate; there is also fighting fewer enemies in more open environments, exploration, a puzzle, a boss battle and an arena battle mode separate from the rest of the demo. Enough to tell me that I would not get bored from doing one thing over and over again for the vast majority of the full game. Had the demo focused entirely (or almost entirely) on just one of those elements, I would have gone back to ignoring it, never learning that the full game would be must-own.