The following was published in the December 2009 issue of Game Developer magazine…

The surgery game Trauma Center was one of the earliest examples of how the Nintendo DS could change our industry. By turning the stylus into a scalpel, the designers let players immerse themselves into the role of a doctor as never before. Unfortunately, the game simulated the pressures of actual surgery as well by presenting staggeringly difficult, time-pressured levels.

Failure blocked the player’s progress, which proved to be a fatal flaw for the game because there were no difficulty levels at all – no way for the player to decide what level of challenge was appropriate. Considering the wide demographic of gamers today, from young children to seniors, this decision doomed the game to a tiny slice of the DS’s audience.

Challenge has always been a core component of game design. However, after video games left the arcades – in which quick difficulty ramps were a necessity of doing business – most designers realized that their games could appeal to more people if they tailored the challenge to meet the needs of the individual user.

Dynamic Difficulty

Call of Duty 4, for example, measures the player’s performance during the training level to suggest an appropriate difficulty level. Other games – such as Left 4 Dead – have developed dynamic difficulty algorithms which adjust enemy spawns and health drops to the player’s current situation and demonstrated skill.

However, dynamic difficulty can be a tricky proposition as – similarly to AI cheating – if the player can see the invisible hand controlling the challenge, the spell is broken. Players need to perceive that they are improving against a fixed measuring stick. The RPG Oblivion turned off many people by scaling the weapons and skills of enemies directly in relation to the player character’s level.

Once this mechanic became obvious, many absurd strategies emerged, such as never leveling up to ensure that enemies always stayed weak. More significantly, this dynamic ruined one of the core features of an RPG – power progression. After developing advanced characters, players enjoy easily brushing aside monsters which earlier in the game could have destroyed them.

Elective Difficulty

Indeed, the core mechanic of RPG’s – that the player character grows slowly in power after each successful battle – can be seen as a way to give players the ability to adjust the game’s difficulty themselves. Gamers who feel comfortable with the combat system can push ahead through levels at the edge of their abilities while players who prefer a more comfortable experience can grind their way to overpowered characters before proceeding. Most importantly, this system puts the player in control, not the designer.

Although selecting a difficulty level at start was a simple, early innovation, only recently have games allowed players to switch between them during normal play. On every third death in Ninja Gaiden Black, players could elect to drop to “Ninja Dog” mode, which weakened enemies but also forced Ryu to wear pink ribbons as punishment. This mechanic – minus the mockery – was quickly adopted by other games, such as God of War.

Indeed, elective difficulty itself can be a core gameplay mechanic. The browser-based Desktop Tower Defense has no difficulty levels at all but does allow the player to speed up the game (and thereby increase the challenge) by triggering attack waves prematurely. Then, the final score is calculated from not just how many enemies were destroyed but also from how quickly the game finished. Therefore, beating DTD on the default speed is just the beginning as players must learn how to master the speed-up mechanic to start improving their scores.

Orthogonal Challenges

While the difficulty levels of Thief do not determine the number of guards nor their awareness on a given level, they do specify the challenges the player sets for herself during the level. For instance, the requirements of Easy may only be stealing a certain number of jewels and artifacts while Hard also necessitates finishing the level without killing a single guard.

These different modes suggest orthogonal challenges within the same game, a smart way to extend a game’s life for the hard-core. Other official examples include the One City Challenge and Always War options in Civilization 4 and the Hardcore mode (with permanent death) in Diablo 2. Indeed, Xbox Live Achievements provide a fantastic infrastructure for adding new challenges via unorthodox goals to games that might otherwise no longer interest core gamers.

Furthermore, other settings can adjust the challenge of a game without changing the difficulty, per se. For example, a real-time strategy game could have both a difficulty setting and a speed setting, so a player could try a more difficult AI but at a slower speed if he did not enjoy time pressure. One sadly forgotten setting is the complexity option that appeared in earlier games, such as M.U.L.E. and Lords of Conquest. This option provided a simpler version of the game – with less types of resources, for example – but still with a fully-capable AI that could provide a challenge for new players.

Challenge and Punishment

However, some games choose to punish players on top of giving them a fair challenge. Games without generous save systems, for instance, are vulnerable to being ruined by challenging sub-sections, which might require multiple attempts to pass. If a player needs to repeat a lengthy but easy section (or, more shamefully, a non-skippable cut-scene) before getting to the difficult bit, the game is punishing the player instead of challenging him.

One of the most elegant solutions to this problem was the time control mechanic in Prince of Persia: Sand of Time, in which the player is able to rewind past mistakes a limited number of times to try again. This system reduced the overhead of repeating a difficult jump to a relative minimum while still retaining tension because of the finite number of rewinds.

Another example of reducing punishment can be seen in the history of MMO’s. World of Warcraft famously reduced the penalty for death found in its predecessors, such as Everquest and Ultima Online. By removing corpse runs and experience loss, WoW enabled people to play the game they way they wanted to play it. Instead of only attacking easy monsters which would never cause the loss of experience or loot, players could attempt a difficult battle knowing that, in the worst case, they would be warped back to a safe location.

Thus, games with severe penalties for failure can actually warp the core gameplay by strongly encouraging players to always choose the safe route. Defense of the Ancient, the popular mod for Warcraft 3, rewards the opposite team with gold every time a player is killed, which makes bumbling new players extremely unpopular with their teammates. This simple dynamic makes the DotA community notoriously nasty and unpleasant, even by the meager standards of the Internet.

After Punishment

The strategy/puzzle hybrid Puzzle Quest took WoW‘s forgiving nature to the logical extreme by removing all forms of punishment from the game entirely. Players are even rewarded for losing battles, albeit much less than they would be for winning them. In fact, this mechanic has an interesting side benefit; Puzzle Quest has no need for a visible save system. Because players are never penalized in any way, the game can comfortably auto-save after every battle or action, knowing that a player will never feel the need to revert to an earlier save.

Such a forgiving system is not for every game. Bioshock used a similar mechanic by respawning dead players for free in Vita-Chambers placed throughout the game. Furthermore, enemies health rates were not reset on a player respawn, which meant that the player could chip away at any enemy with any weapon, including the wrench, if she was willing to die and be reborn enough times. This feature felt like an exploit to enough players that Irrational eventually patched in an option to disable Vita-Chambers.

However, the problem may have been with the expectations of Bioshock‘s intended audience instead of any fundamental flaw with the respawn mechanic. Lego Star Wars uses an identical mechanic, which is perfect for the target audience of a dad and a son playing together in a forgiving environment. For Bioshock, core gamers expected the game to force them to use advanced strategies to progress instead of an easy out.

Perhaps the best solution is to always allow players to progress but to rate their performance against some constant metric. Elite Beat Agents hands out letter grades of S, A, B, C, and D for each song performance based on the player’s timing. The game continues as long as the player finishes the song, but few will not want to go back to try and improve. If Trauma Center had only adopted such a simple system, the game may have become more than just an interesting footnote. Designers should take care not to head down the same dead-end.