Now that we’ve covered the two forms of progression, there are other elements that affect both in different ways. Additionally, the two aren’t mutually exclusive, and can interact in different ways. In this article, we explore these topics.
As evidenced by games like Doom and Singularity, both kinds of upgrade progression can benefit from hiding certain upgrades, money or tokens in secrets hidden around the map. Doom often hid weapons in secrets (chaingun hidden on the second map, rocket launcher on the third, etc.), along with other very helpful items. Singularity was one of those games that featured both a money and token system, and often hid BOTH across maps. I like this because it can draw the player further into the game, making him explore around and appreciate some of the graphical details he might not notice if he was just trying to get to the end. I think Dead Space could’ve benefited from this to draw the player further into the game (something important for survival-horror shooters like that), but all of the credits and power nodes were somewhat obvious.
Unfortunately, hiding upgrades or some form of upgrade currency in secrets can be hard to pull off correctly. Secret weapons can potentially wreck the progression curve in your game, to the point where there really doesn’t feel like it’s easing you into the progression at all. In Duke Nukem 3D, you can literally get every weapon available in the first episode in the first map. It’s balanced by the fact that ammo for some of them is limited so you can’t use the RPG or pipe bombs as often as you might want, but there’s still not much actual progression there. Quake 2, over the course of the much-longer game did introduce weapons more slowly, but still did have more advanced weapons hidden in secrets. The super shotgun was first available in a secret map in the first unit (essentially halfway through the unit); the next earliest is a secret at the very end of unit 1; the first time it’s obviously available is at the start of unit 2. The first rocket launcher is in a secret at the start of unit 4. The first time you can find the BFG is a secret in unit 6 (out of 8). It gets around that problem of ruining progression by spacing them out quite a bit more, so it still feels like a slow progression.
A potential problem with hiding currencies to upgrades in secrets is that it’s tricky to strike a balance with how much to hide, and how much to keep open. In several games that hide currency in money systems, especially (Singularity, Red Faction: Armageddon, etc.), very sharp players end up with a massive surplus of them, even if they’re used for other things, like Deus Ex: Human Revolution. One game that did this better was Hard Reset, where a certain amount of points gets you an upgrade. However, not many of those upgrades made you more powerful (beyond the obvious two or three that you’ll likely get first), so it didn’t mess with the game’s balance much. Tokens end up working better in this regard because they can be balanced more easily than amounts of credits. When you hide money, you’re hiding some abstract amount; it could be big part of a small upgrade, a small part of a big upgrade, etc.. When you hide tokens, that’s a whole upgrade (or half of a better upgrade, or whatever)! You can more easily plan for the player having this amount of upgrades (what’s in plain sight) while accounting for the player having all of the possible upgrades. This is one of the main strengths of the token system.
Another consideration is how open-world the game is. By open-world, I mean the game has defined objectives, but doesn’t care how they’re accomplished or whether you do them quickly, and even has optional side-missions. Crysis (the first half) and Red Faction: Guerrilla, for example, had gameplay like this. Because the game is open-ended by definition, a linear progression is difficult to pull off correctly. How can you know a player will be at this location to pick up this new weapon? Crysis (and Crysis: Warhead) occasionally had caches of weapons designated as secondary objectives, usually with a powerful new weapon as an introduction. Red Faction: Guerrilla had a combination between player-driven and linear progression; after completing certain missions, new weapons become available to unlock with salvage (money), and occasionally new enemy soldiers show up with new weapons (which you can pick up). Because you can’t introduce weapons in Quake 2’s style of linear progression, you have to tie weapons to particular events, or risk the player just missing the progression.
Player-driven upgrade systems can work better in open-world games, though, because the player might be able to go back and pick up upgrades that might be needed for some part of the game. For example, in missions in Red Faction: Guerrilla where you have to capture a vehicle but you don’t have an Arc Welder (makes vehicle capturing much easier because it kills the driver without damaging the vehicle), you could go looking for salvage to unlock it beforehand. It’s easier to balance around, since the developer can assume the player has some kind of upgrade, because the player could go somewhere else, get that upgrade, then return. This is one instance where I think allowing the player to grind for infinite upgrade currency can work, but I have never liked it for more linear games because it encourages the player to sit in one particular area, often in a style of game that encourages the player to keep moving forward.
One other factor with player-driven upgrades is to prevent the player from getting particular upgrades until he’s progressed to a certain point of the game. In Wolfenstein 2009, you can upgrade weapons and Veil powers with gold hidden in the game. Many more powerful upgrades aren’t more expensive than previous ones, but they require certain levels be completed before you can purchase them. Similarly, Red Faction: Armageddon has certain tiers of upgrades. The first tier is available from the start, but the higher tiers with more powerful upgrades are locked until you reach certain milestones in the single-player game. Another take on this is the schematic system in Dead Space and Singularity; You don’t even know about these upgrades until you find schematics hidden in the levels (in Dead Space, these take up inventory space, so you actually have to decide if you want it). In Dead Space, they were fairly obvious, but many of them were hidden in Singularity. This system adds a tone of linear progression to a player-driven progression system; preventing the player from getting too powerful, too early in the game, and slowly introducing him to new powers.
Something that might surprise you is how upgrade progression and story go together. One way in which Red Faction: Armageddon feels horribly unfinished is that some of its upgrade system isn’t explained in story at all. In the backstory for the game, it says the main character has been upgrading the Nanoforge bit by bit, so this is simply a continuation of that. What isn’t explained, however, is why certain tiers of upgrades are locked, why an upgrade to the Nanoforge lets his guns store more ammo, or things like that. While it doesn’t affect the gameplay, things like this can hurt the player’s immersion if there are widely unexplained and implausible elements like this, which can lessen enjoyment (if the player cares about that). It might not be very serious, but again, worth consideration.
As you can see, you don’t have to commit to either a player-driven or linear form of progression. In fact, I think the best method is a combination of both; mostly linear with some minor player-driven upgrade system. Red Faction: Armageddon, though I think it was rushed, did have both used quite well. As you progressed through the game, you found new, more powerful (or more useful) weapons. Additionally, you found salvage (currency) for purchasing upgrades for your Nanoforge (granting new usable abilities and upgrades for your character). You could customize your weapon loadout to fit your play style, and upgrade how you wanted to fit that; you could take melee weapons and explosives and upgrade your explosive and melee damage, for example. Or pick a longer-range loadout, increase your damage with headshots and the clip size of your weapons. It locks some more powerful upgrades until you’ve progressed a certain way into the game, as well, so you have to progress in power as the game steps up its difficulty, and you are prevented from beelining to the powerful upgrades you want. Additionally, the game also got harder because they actually assumed the player did get some upgrades (and it’s still possible to beat the game if you don’t even get any, though it is much harder), and indeed the game actuallygives the player several upgrades in the form of weapons, which the player uses more often than anything else.
This also isn’t limited to shooters; RPGs, strategy games and some other genres all feature progression. Think of Starcraft 2, where each new mission in the campaign introduced you to a new unit you can use (linear), and can upgrade certain things outside of missions (player-driven). Starcraft 2 also did a very good job working it into the story, as well, with explanations for how each upgrade works in the game’s lore, and the reasons why you’re getting these new units in the campaign. Level-based RPGs also blend the two very nicely, with Baldur’s Gate and Torchlight being perfect examples. Progressing through the game gets you experience and loot, experience gets you levels, which increase your power. Just about everything I’ve talked about about in this article works with these types of games as well.
Upgrading the player is almost essential to these genres of games. Shooters can get dull if the player never increases in capability in some way, and RPGs are entirely built around it. In order to implement a proper system for it, you have to understand all the different ways a player can acquire those upgrades. I don’t believe for a second that this is everything that affects how he gets upgraded (it was all I could think of), but hopefully these articles are a good place to start in how you design your system.