Limited Resources and PowerUp Design

The world is run­ning out of oil. Clean water. Top­soil. Ozone. These rep­re­sent seri­ous resource prob­lems about which I know … lit­tle. Do your research, and then shop or vote appro­pri­ately. On the other hand, a cer­tain prob­lem of dig­i­tal lim­ited resources has con­sumed much of my time of late.

No top­soil, sure, but the trade­off is giant worms, magic spice, psy­chic pow­ers, and FTL travel.

First, let me refine my topic. I’m not con­cerned with game cur­ren­cies: money, crys­tals, expe­ri­ence points, or ammo. Bar­ring sig­nif­i­cant error, those resources per­sist through a game and remain valu­able. With such in-game cur­ren­cies, the designer makes an implicit promise to the player that cur­rency will flow in (insert oblig­a­tory “the spice must flow” ref­er­ence). Thus, the player might as well spend it, since he’s going to keep get­ting more. Games that break this promise are likely to be con­sid­ered poorly bal­anced or frus­trat­ingly hard­core. How play­ers spend those cur­ren­cies rep­re­sents major strate­gic decision-making, and the game incen­tivizes the player to acquire and spend cur­rency for a vari­ety of ben­e­fits. As a side note, vir­tual cur­ren­cies have never been more impor­tant in games. They form the back­bone of half of what con­sti­tutes game design going on right now.

In any event, cur­ren­cies aren’t what I’m focused on. The game I have in devel­op­ment has made me curi­ous about tac­ti­cal decision-making (as opposed to strate­gic). How and when do play­ers use items and abil­i­ties that we broadly call power-ups? In this cat­e­gory, I’m includ­ing con­sum­ables, grenades, buffs, cooldown-based abil­i­ties, limited-use weapons, spe­cial ammo, etc. Regard­less of the incar­na­tions in an indi­vid­ual game, I want a bet­ter under­stand­ing of how play­ers choose to use their items and abil­i­ties. What trig­gers the deci­sion? That’s a ques­tion I’ve been dis­cussing with play­ers, devel­op­ers, and playtest vic­tims. How to best design power-ups for our games?

A core prob­lem with power-ups is there is no guar­an­tee of resource replen­ish­ment. Bar­ring the use of a hint guide or online walk­through, the player can’t pre­dict when he or she will find a power-up. The player can’t make informed deci­sions. In more com­pet­i­tive mul­ti­player, the player may learn where objects spawn, but per­haps not when, or if they have been claimed. So, point one about good power-up design should be: keep the player as informed as the game design will allow. Try to intro­duce greater reliability.

A sim­i­lar lack of prog­nos­ti­ca­tion obscures when to use a power-up once acquired. The game’s nar­ra­tive, if such a thing exists, can pro­vide clues that “this is a high chal­lenge moment.” That can do the job, to be sure. And if the power-ups only exist in order to be acti­vated dur­ing boss fights, so be it. The down­side? The more explicit we get here, the less agency we’re reserv­ing for the player. If a chal­lenge explic­itly calls for power-ups, and is bal­anced to assume power-up usage, what have we gained?

So, an essen­tial prob­lem is the player has an incen­tive to hoard power-ups, like some unfor­tu­nate crea­ture from the real­ity tv show of the same name. An imag­ined chal­lenge always lurks in the hazy future. So con­sum­ables pile up in the inven­tory, often lan­guished until the end of the game. How to stop hoard­ing? Here’s the irony. Ask any player, and they’ll tell you they need more inven­tory space. Many role­play­ing games embrace this, cre­at­ing an econ­omy in which play­ers spend cur­rency (even real-world cur­rency) for the priv­i­lege of more inven­tory to man­age. Hmmm.

Good luck find­ing the health potion, hoarder

Back to design. So what is the point of power-ups? Is the value in find­ing them, or using them? If the acqui­si­tion is the end, the specifics of how we use or store them is barely rel­e­vant. Why use power-ups as pure reward? We have other, less util­i­tar­ian, devices for that — hand out expe­ri­ence points, game cur­rency, cin­e­mat­ics, or achieve­ments. Power-ups allow a player to become more pow­er­ful than the game bal­ance gen­er­ally allows. To exceed nor­mal lim­its. In as much as the game design sup­ports choice, a power-up rep­re­sents a chance for the devel­oper to make the player feel like his choices make a dif­fer­ence. For the player to demon­strate his intel­li­gence and mas­tery of the game.

If large inven­to­ries present twin dan­gers of hoard­ing and inter­face night­mares, sim­pli­fi­ca­tion offers hope. My playtest­ing is show­ing that with tight inven­tory max­i­mums, play­ers use more power-ups. At the far end of the design spec­trum: a max inven­tory of zero. Play­ers acti­vate power-ups in the act of find­ing them or walk­ing over them (e.g. the Mario approach). It solves the prob­lem, but it does takes away most of the decision-making. A player can remain adja­cent to a power-up until it is needed, but this con­fines player behav­ior to a great degree. Good for some games, espe­cially more casual games.

What’s next after an inven­tory of zero? Well, one. Left 4 Dead offers a solu­tion revolv­ing around an inven­tory of one for offen­sive power-ups (grenade-like objects) and defen­sive power-ups (health packs). Inven­tory remains vis­i­ble onscreen and hence obvi­ous at all times, con­fronting the player with options to recover health (with voice-over reminders from AI) or throw the dyna­mite (with audio cues from fast-paced action music).

After one, we arrive at few. The best solu­tion I’ve found along this line is in the now-classic MMO, City of Heroes. The “inspi­ra­tion” sys­tem remains onscreen and presents a rea­son­able num­ber of options to the player with­out sig­nif­i­cant inven­tory man­age­ment. The temp­ta­tion, though, is to save valu­able inspi­ra­tions (such as “awaken”). And  even at the low lev­els when the inspi­ra­tion inven­tory cap is small,  play­ers hoard these power-ups, wait­ing for the per­fect moment. Which never comes. Unless it’s a heal or res­ur­rect. We do seem bet­ter, as play­ers, of respond­ing when defen­sive power-ups should be used. A low health bar is an easy stimulus.

Offen­sive power-ups need more thought, and we may need to aban­don the inven­tory metaphor altogether.

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