The second kind of progression, player-driven progression is where the player picks and chooses what upgrades to get. It’s usually accomplished through a purchase system of some sort, though some first-person shooters with role-playing elements use this for their RPG mechanics (Deus Ex: Human Revolution is a great example of a game with a shooter’s balance and gameplay with RPG mechanics, as opposed to Fallout 3 which is a first-person RPG with guns).
The best example of this is the original Dead Space, where every single weapon (except the first weapon, the Plasma Cutter) and upgrade has to be bought. Weapons and new suits (armor and inventory upgrades) are purchased with credits you find scattered in maps or dropped from enemies, while upgrades to those weapons and to yourself (air meter, health or other categories) are accomplished through power nodes you find or can buy with a large amount of credits. The player does find schematics throughout the game for new things that can be unlocked, but that’s not as much linear progression because it’s up to the player to actually unlock those himself.
There are two methods of currency I’ve seen in recent games for purchasing upgrades in this manner. The first is where it takes a certain amount of some common resource (which I’ll refer to as a money system) and the second is where it takes just one of some much-rarer resource (a token system). Dead Space uses both; it uses credits as a money system (used to buy new weapons and suits), and power nodes as a token system (used to upgrade those weapons and yourself). Often times if a game has both, it’ll let you use your money to purchase a token, as Dead Space does by letting you buy power nodes with a large amount of credits (Deus Ex: Human Revolution and Singularity are good examples as well). There are some benefits to both.
Money systems allow players to get a more steady stream to inch more steadily to an upgrade, so they feel like there is constant progress towards it. It can let the player gauge how long it will take to get a particular upgrade. If you hide money around maps to reward players for exploring (like is often the case), you can also add a surplus to reward inquisitive players. Now, the big problem with that is that you can often have a big surplus towards the end of the game. In Deus Ex: Human Revolution (even without the DLC that gives you 10,000 credits), you can still get enough credits to buy the ammo you might need as you need it, weapons and weapon upgrades you want, and all the praxis points you can buy, and still have a surplus at the end of the game. Also, when I talk about money systems, I mean specifically referring to upgrades; not buying ammo, health items or things like that. However, in these games where you can use currency for items like that, you can often have a large surplus of those items anyway.
Some games tie the money system in with killing monsters. In both Binary Domain and Crysis 2, for example, that was the only method you have of getting that currency. You might have to be careful with this, though, if you have potentially-infinite monsters because that could allow the player to just farm money. In the case of Crysis 2, there were limited monsters and only a few varieties gave you that currency. Binary Domain only has infinitely spawning monsters in one or two spots, but you definitely do not want to stick around there because you can run out of ammo or other resources. There are some arguments about this, but I don’t think it’s a good thing to let the player farm money for upgrades in shooters, specifically. In older RPGs farming money for armor or weapons was part of the gameplay and no problem at all, but I feel like it’s a problem in shooters because it can screw up the game balance. If the player can spend some amount of time when a group of upgrades become available getting all of those upgrades, then he can screw up the balance. There are arguments that if the player wants to dedicate the time to that then he should be allowed to, but player-rights-versus-developer-design is another article. I will speak about a game that gets around this problem in the last article of this series.
Make sure there aren’t problems with how you give the player this money, if they get it from killing monsters. Binary Domain just adds it to your counter, but Crysis 2 has some problems. Monsters just drop it when they die and you have to walk to their corpses to collect, but it’s actually just a separate pickup that’s very hard to spot, and if you don’t pick it up within a certain time period then it vanishes. In a game that rewards you for playing carefully, you don’t want your rewards vanishing. It would have gone better if the bodies themselves gave the currency (would’ve fit the story better, as well), and had some more obvious indicator that the currency was available from that body. Dead Space, I think, got it right; monsters can drop credits when they die, but you have to pick it up, the pickup is pretty obvious, and they never vanish.
Token systems, however, feel a lot simpler; you find an item, you can buy an upgrade. However, it’s a trickier balance between how important each token should be in terms how strong the upgrade is, or how rare the tokens are to get. While this is a subjective opinion-piece, one other pitfall I think token systems can fall into is when a single token won’t buy you the upgrade. Dead Space had an upgrade tree with its power nodes where you could only move onto more upgrades by fitting power nodes into adjacent slots to that upgrade.
Unfortunately, this meant most of the power nodes you were using… weren’t being spent on upgrades, they were spent on “empty” slots to get closer to slots that actually contained upgrades. With token systems, you want to give the player more of a payoff every time, because he’s usually working so hard to find or acquire these tokens (though they were more common in Dead Space, but you still probably weren’t going to be able to max out a whole weapon and your suit). Singularity had this to a much lesser degree with Weapon Tech upgrades. Each weapon had three categories (usually reload speed, damage and clip capacity) that could be upgraded twice. The first upgrade takes one Weapon Tech, and the second upgrade takes two. Deus Ex: Human Revolution did the same thing, with some augmentations taking two praxis points to unlock. That’s not nearly as bad, however, because the player is still getting that payoff because it requires that many to get the upgrade before it takes both, rather than having to put one in specifically for nothing. It’s like the game telling you “Okay, you just spent that point and got nothing for it!” rather than “Okay, this upgrade is good enough to take a bit more than the usual cost to upgrade.” It also blurs the difference between money and token systems, which should be distinct from one another because they have their own strengths and weaknesses; when they combine, they get most of the weaknesses, but the strengths don’t usually combine as well.
Another major difference between money and token systems is that the upgrades have to be balanced differently depending on which you use. With a money system, you can make an upgrade more powerful or more useful than others, and then balance it by making it cost more than other upgrades. For example, Singularity had several very useful upgrades (more maximum health) that cost more than others, and some that are downright useless (more breath underwater) but didn’t cost much. With token systems (with every upgrade costing one or maybe two tokens), the upgrades have to be balanced around that, so they’re roughly equivalent. This works better with games that allow multiple play styles, like Deus Ex: Human Revolution, as all of the upgrades (with a rare exception) are equally useful, just in different ways.
There’s one major downside I’ve found to this method; it’s much, much harder to balance your game if you exclusively use this method. Several people say Dead Space gets too easy as the game goes on, and this is because the developers can’t assume the player has any specific upgrades. The developers have an idea that the player could have the level 5 suit at the end of the game, but he very well might not have bought it, or might not have even picked up the schematic. Though slightly harder, every enemy can be killed with the Plasma Cutter because the developers made sure you can, as they just don’t know what weapons you bought and what you haven’t when they place those monsters in the map. Granted, while the game is pretty hard if you don’t get any upgrades, if the developer assumes the player has a certain level of strength, he risks the game being unfinishable because the player might not have what’s necessary to progress. Again, at the end of this series when I bring all of this together, I will give an example of one game that gets around this problem perfectly.
The good thing about this system is that it gives the player the freedom to upgrade what he wants to upgrade. If he’s good with a particular weapon or if there’s something keeping him from using it well, he can upgrade it. If there’s a weapon he doesn’t like the look of, he can skip it. It can potentially let the user have the game cater to his play style, rather than forcing a particular play style from him. Deus Ex: Human Revolution is famous for having so many upgrades catering to different play styles so you could run through the game as an ordinary shooter, as passive stealth, or as an assassin. Some of those upgrades were outright useless, but the majority allowed you to play in different ways.
An increasing amount of shooters over the last decade have been using player-driven progression more and more. If you’re implementing this kind of progression in your game, it should be carefully thought out and balanced. I hope this breakdown helps readers to understand this system a bit better.