Unlocks (unlockable items) are an important part of modern games. Much like achievements, unlocks can be much more than an easy way to pat the player on the back: in fact, they're basically just achievements with in-game rewards.
As with any other aspect of game design, there are good ways and bad ways to design unlocks. Many devs seem to throw them in as an afterthought, even cropping out key aspects of the gameplay apparently at random to have something to offer the player as a reward. But is it possible to make an unlock system which enhances the overall game? Let's take a look at a few possibilities...
Guide the Player
It might seem counterintuitive, but one of the best ways of using unlocks is to restrict players' options.
It's natural to want to present the player with all the cool things they can do in your game, but (as with achievements) it's vital to ease the player into the game, preferably teaching one basic gameplay element at a time.
Let's look at the first level of Plants vs. Zombies, which is an excellent example of how to merge an unlock system into gameplay.
- You start off with one plant type available. You don't have to worry about resources, or plant combinations, or efficiency: you just plant.
The first level is almost impossible to lose. The next few levels "unlock" the remaining rows of gameplay, opening the "real" game. Throughout the game, different zombies start attacking you, which keeps the game interesting. And importantly, every level you unlock a new plant type.
This unlocking of plants is a driving factor of the game: not only is it a very obvious reward, but it slowly exposes the player to new gameplay elements, one level at a time. In other words, the tutorial of the game is the entire game. By the time you've completed the game, you've hopefully mastered the various plants available - and so you're given the option to play the game again, but this time with all plants available from the start.
Another game which has a "slow tutorial" aspect is Desktop Dungeons. In this mini hack-and-slash RPG, the player is given a mere four classes to start off with: Fighter, Priest, Thief and Wizard. These classes are reasonably straightforward, and are an excellent introduction to the basic game tactics.
If you complete the game with the Fighter, then you unlock the Beserker class, which requires a moderate level of skill to use effectively. Complete the game again, and you unlock the Warlord: a high risk character that gains hugs bonuses from being near death. These characters are not necessarily better or worse, but the player must demonstrate skill before being given access to them.
It is partly for this reason that many games have an unlockable "nightmare mode" difficulty - not only does the additional mode provide more game content, but a player who jumps straight into it might find themselves getting destroyed repeatedly.
Reward the Player
Giving the player new unlocks is also a great way to reward them. Unlocks can often be tied to achievements. In Team Fortress 2, acquiring enough class achievements unlocks that class's additional weapons. It's worth noting, though, that the new weapons are not necessarily better than the ones they start off with: in fact, many pro players claim that the stock weapons are amongst the best in the game.
This is an important game balance choice: balanced weapons (such as in TF2) keep the playing field relatively even, and encourage new players into the game. Imbalanced weapons (such as in Battlefield) encourage more of a grind - thus rewarding players who put time and effort into the game, but possibly scaring off newbies. In order for the player to remain competitive, the game may become work.
This is the basic model of nearly all MMOs: players "unlock" (or "earn") new skills, levels, abilities and weaponry. By putting more hours into the game, players hope to become more powerful. Neither option is necessarily right or wrong; they just each bear a different core audience in mind.
The reward factor in MMOs cannot be understated either: when playing a new character in World of Warcraft, you can level up from 1 to 2 in five minutes, experiencing a very rewarding "ding". Getting to level 5 might take an hour, as each level is slightly more difficult to achieve than the last. Hitting level 70 or 80 may take days or weeks.
This reward mechanic can often be used in place of a level system outside of MMOs. Rather than progressing through different levels, the player progresses through the same level but under different conditions. The previously mentioned Desktop Dungeons does this to an extent, but a better example would be Snakes on a Cartesian Plane. A rather simple snake clone, the true genius of this game is in offering the player different gameplay styles, and changing the game's focus from "collect points" to a "find cool new unlocks".
Don't Punish the Player
Many developers see unlocks as free "fun" points they can insert into their game. While players are generally willing to unlock all the content if they enjoy the game, it is counter-intuitive to restrict basic gameplay elements.
One such offender here is Super Smash Bros Brawl, which restricted some fan favourite characters such as Sonic to the unlock system; to make matters worse, unlocking these characters often required hours of single player content (in what is primarily a party game). While it makes a certain amount of sense to restrict levels to the unlock system, the characters are such an integral part of the game that players may feel cheated when they find they can't play them. If a group of friends sits down with a new copy of the game, they don't want to be forced to grind content in order to have fun.
Free-to-play games are often taking this route as well: rather than offering the player a fun game with additional optional content, they will fall into a "pay to win" scenario or simply be unplayable without depositing large amount of cash in-game. EA's Real Racing 3 recently exemplified this, with almost all in-game elements requiring payments. There was considerable backlash, with many claiming that while the gameplay was excellent, the game itself was ruined by in-app purchases.
Where Do We Go?
So, much like achievements, unlocks can be used to change player behaviour. The desire to "level up" can be a driving force. As long as the player is having fun, they will keep chasing after the carrots you dangle in front of them - so it's important to make sure that unlocks are fun and feel like a reward, rather than the designers simply spoon-feeding them gameplay elements.
Rewarding the player is the most obvious aspect of unlocks, but much more attention should be given to guiding the play. It's really the underdog of gameplay design, and its something that really deserves more attention. When you guide the player, then you can set the game progression to a pace you like. You can negotiate which levels the player has access to, which enemies they can fight, and what abilities they can use, and do so in a way that feels natural and the player has time to become accustomed to.
It's worth closing off with a quick overview of one of the most famous unlock-based series: The Legend of Zelda. The basic gameplay design hasn't changed much over the years, so lets take Wind Waker as an example:
- The player starts off on a small island, where they learn basic gameplay elements such as moving, attacking, carrying and using items.
- Throughout the game, they find dungeons which unlock new weapons and items, such as the boomerang or iron boots.
- Once they have unlocked all the items, they can make their way to the end game.
Despite being a very different style of game, Zelda is - in this regard - almost identical to Plants vs. Zombies. Theoretically, the whole game is open to the player from the very start, but the more difficult areas are only available once the player has appropriate item - and, more importantly, has learned how to deal with the respective enemies. And, once again, the "tutorial" runs nearly the whole length of the game. Every dungeon is basically a tutorial on how to use the newly acquired item.
In fact, every item room in Wind Waker locks you in, and the only way to escape is to use the item you just found. The game forces you to understand what it is you've just picked up, so that once you leave you won't be confused by new puzzles.
Don't be afraid to toy with unlock systems. While not every game will be immediately improved by simply including unlocks, they can be used to influence the gameplay in more subtle ways than simply creating a level select screen. By making your worlds feel more open, they become more familiar and alive. You can let players revisit old areas with newfound powers, or you can keep pushing them through more difficult challenges. A light touch guiding the player is almost always more preferable than forcing them down a certain route, and the gameplay will feel smoother and more natural as a result.
And finally, it's worth taking a look at Upgrade Complete, a fun little Flash game which takes an interesting (and satirical) look at unlocks in gaming.