We designers are our players' greatest allies. Sure, we expend considerable effort crafting enemies and traps that present increasing levels of challenge for the player, and sometimes we get carried away and don't stop until the latter stages of the game require the skills of a minor deity. But at the same time, we mitigate the impact of these growing challenges by giving the player new powers and abilities to toy with.

Recently, I have been thinking about the properties of the various kinds of power-ups we see in games. I have identified three orthogonal axes of design (to follow Harvey Smith's very useful terminology) that can be used to classify them into a cubic grid. I will present the results of my analysis in a three-part article; the first axis, Activity/Passivity, will be the topic of this month's installment, while the other two will be covered in the next issues.

Note: for the purposes of this discussion, my definition of "power-up" will include everything that improves the player's character, army, or palette of options. Thus, magic-resistant armor, bonus hit points, new and improved units, inventory items, and special combo moves will qualify just as naturally as super-jumps and explosive ammo.

First Axis: Activity / Passivity
A power-up's position along this axis measures how much or how little its activation depends on a conscious decision process on the part of the player. As we will see, different levels of player involvement appeal to different audiences and are suited to different circumstances.

Passive
A passive power-up is always on, no matter what happens during the game. In other words, once the power-up has been acquired, the player can just forget about it – he'll receive benefits without having to perform any specific action to do so, as often as necessary, until the power-up wears out. Examples of passive power-ups include hit points, a temporary invulnerability to poisons, area keys in most platform games, and better arm strength in a football game.

Passive power-ups are an effective tool in every designer's arsenal because their presence or absence can serve as barriers and guides for the player. Sometimes, the barriers and guides are explicit: a door is locked, so an area of a level is off-limits until the player has found the key (and presumably accomplished other preparatory tasks). A subtler approach is just as effective: a fire-breathing dragon or a wide ditch can push players away from an area until they have acquired fire-resistance or super-jumping abilities.

Extensive use of the passive power-up is especially well suited to casual gamers and children, because a passive power-up constitutes an effective reward in itself: it confers new abilities, and it requires no effort. No need to figure out how to use a new weapon or how to combine ingredients into a potion: being able to walk through a pit of lava without catching fire is cool right away.

However, passive power-ups do have a serious drawback: they remove strategic choices from the player's control by making all tasks of a given class automatically easier.

Suppose that Gorg the Unready, 2^nd-level barbarian, has strolled through the first few levels of a fantasy RPG in typical barbarian fashion, i.e., through a button-mashing, hack-and-slash slugfest. But now, Gorg suddenly finds himself standing in front of a sleeping dragon of massive proportions.

Gorg's trusty Plastic Spoon of Maiming wouldn't score much more than 1 point of damage in every round against such a behemoth. As a result, the designer has planned a really clever way for Gorg to sneak past the sleeping dragon without getting caught. If the player examines his surroundings carefully and figures out the optimal strategy, he'll avoid the fight AND feel wonderfully smart.

However, if Gorg has somehow achieved 100% fire resistance through the acquisition of passive power-ups, then nothing would prevent him from spending the next five hours bashing the dragon to death with his spoon, because the enemy would have no way to fight back – the passive power-up has removed the challenge and the fun from the encounter.

Since using passive power-ups requires no skill, the designer must be careful that they do not provide too many easy ways out of interesting challenges, or the game will quickly lose its flavor.

Active
An active power-up is one that the player must put into action himself at the precise moment of need. New spells, demolition charges and a unit-building budget are all good examples: if Gorg the Unready is waylaid by a pack of feral sparrows, no fireballs will mysteriously materialize out of thin air to extract him from the predicament unless Gorg actively casts a Fireball spell himself.

Active power-ups provide an excellent way to give players tools with which to figure out solutions to problems. You just found a length of rope and a cowbell? Tie them together into a long-range weapon to whack a deaf monster upside the head while staying out of reach of its giant tentacles. You need a Positronic Hyperspatial Relay? (Who doesn't?) Grab the components in the spacedock junkyard and build it yourself. Simple, yet wonderfully stimulating for the inquisitive player.

However, before one can make effective use of an active power-up, one has to learn how to use it, which isn't always obvious. Sure, a magic missile spell is pretty much self-explanatory, but what about a quirky new RTS unit that can deconstruct enemy buildings and salvage resources? How much protection does it need? Is building a couple of these units and sneaking them into the enemy's base camp to sabotage his war effort cost-effective? More pointedly, is it more efficient than simply blasting him to smithereens, or less so? Who knows?

As a result, novice players may find some of the more arcane active power-ups confusing and refuse to use them – from these players' point of view, the power-up is a wasted design effort. Therefore, when using an active power-up in a casual game, give the player plenty of time to try it out before pitting him against a challenge that requires its optimal use, and especially before introducing the next such active device.

Equipped
Sitting midway between active and passive power-ups along this axis, the most typical of equipped power-ups are passive improvements that may be switched on or off because they are associated with devices that can be lost or exchanged instead of being tied to the player characters themselves.

The classic example of an equipped power-up is the magic item in fantasy RPGs. If you own a suit of Chain Mail of Highly Refined Asbestos and a rare Full Plate Armor of Great Grounding, you can protect yourself (passively) from fire or lightning, but not both at the same time. As a result, using an equipped power-up requires more strategic thinking on the player's part than the passive equivalent, but it also demands much less of his attention focus than an active power. In many cases, the trade-off is optimal.

Equipped power-ups provide support for a variety of gaming styles. If your character packs a flame-thrower, an assault rifle and a Giant Bazooka of Extreme Aggression, he ain't going to sneak into any buildings unseen. Replace the arsenal with night-vision goggles, a silent tranquilizer dart gun and body heat concealment clothing, and you've got an entirely different way of playing the same game. Games that support many different devices may even let players devise strategies completely unforeseen by the designers!

As a side benefit, the placement of equipped items in a game can also serve as a powerful foreshadowing tool. If an astute player finds Snakebiter the Dragon-Slaying Rapier in a dungeon, he will expect to see dragons at some point in the near future. Conversely, some form of foreshadowing of the contents of the next level may help a smart player decide which of his many hoarded items to pack for an adventure. For example, if a soldier's briefing includes eyewitness reports of blue-white lights, short-circuit noises and sparks coming out of the enemy site, he may infer that electric obstacles (some of them possibly malfunctioning) are standing between himself and his mission objectives. Certainly, from the player's perspective, such an in-game acquisition of relevant information is much more fun than running into a room, looking around, getting killed, re-loading, equipping for the obstacles he has just discovered in his "previous life", and starting all over again.

However, one must remember that foreshadowing is a dish best served in small portions. If, in addition to Snakebiter, you plant a fire-retardant suit of armor, a Ring of Fire Extinguishing and a Helmet of Personal Air Conditioning in the same level, that poor dragon will come as absolutely no surprise to even the dimmest of players (and he won't last very long either). On the other hand, if you plant all of this stuff and then fail to include a dragon, you are messing with the player's head, and he won't be happy about it.

Next Issue
In this first part of the series, we have examined the role of the player's active involvement in the gameplay mechanics of power-ups. Next time, we will take a look at the second axis, Permanence/Immediacy, before we wrap up the series the following month. See you there!