Everybody hates the blue shell. It’s become a common memory in the canon of being a modern video game fan: you’re in the lead in a game of Mario Kart, only for a winged blue shell to sail out of nowhere and home in on you, knocking you out for just the brief moment the person behind you needs to sail out from under you and steal your well-earned first place. You, we, have been the victim of a classic comeback mechanic: a game mechanic designed to favor the losing player, in an attempt to shorten skill gaps and prevent a player from being dishearteningly stomped by superior players.
The essentials of designing a comeback mechanic are fairly simple: add some feature that can be triggered by a losing player, or is more likely to be given to a losing player, or is more powerful based on conditions typically associated with losing. This feature grants the player who wields it some sort of unique advantage, designed to allow them to close the gap with the winning player. The most frequently mentioned comeback mechanic in games is Mario Kart‘s blue shell, but they’re out there in the dozens.
The key to comeback mechanics is that they’re very commonly used in games where a tight control of competitive balance is required. However, what this means varies a lot from game to game. Mario Kart, for example, uses blue shells, in conjunction with other items dropped for low-skill players, as a way to leash the higher-skilled players, and prevent them from gaining too indomitable a lead over the lower-skilled players. In this case, the blue shell can be seen as lowering the efficacy of high skill.
However, “maintaining tight control of competitive balance” means something totally different in Ultimate Marvel vs. Capcom 3, which has a comeback mechanic called X-Factor. X-Factor is a one-time use mechanic which increases the player’s damage and speed, by a factor of 10%, plus an additional 10% for each of your downed characters (UMvC3 is a 3-on-3 game, capping your bonuses at +30%). This mechanic is not about limiting skilled players. After all, any player can trigger X-Factor no matter how good they’re doing. Instead, the idea of X-Factor is more directly to prevent snowballing.
You see, a player with multiple characters left is at a competitive advantage to one who only has one, fairly intuitively. With multiple characters, the moveset at your disposal increases by an order of magnitude, you can call in assists, chain your Hyper Combos or perform them simultaneously, in essence your options at any given moment are much wider than someone with a single character. By itself, this fact means that a game of Marvel would be won with the first character down, barring incredible skill. Get one character down, and it’s a 3v2. Ride that advantage, and now it’s a 3v1, and the game is on lock. However, the existence of X-Factor gives a player who is behind a chance to stop their opponent’s momentum on a dime: it can be triggered instantly, including in the middle of combos, meaning that you can take a single hit and turn it into a downed character with moderate skill, preventing your opponent from snowballing into a W.
Sometimes, a comeback mechanic simply needs to give the losing player some time to catch up to the winner. For this, I turn to a comeback mechanic so subtle most people don’t even know it exists, unless they’re playing this game, in which case I usually obnoxiously mention it after about the third cocktail. This game, of course, is pool.
Pool has less of a comeback mechanic and more of a comeback mechanical interaction, which in my opinion is a better choice when possible, because it leaves players with a sense that that’s just how the game “is”, instead of that the designers slapped a mechanic on to babysit bad players (which is not what I think of comeback mechanics, but it’s certainly what some people do). In pool, if you’re just running the table on somebody, you’ll find yourself with a problem, quick: you only have so many shots left available to you, and the other player’s balls spread all over the table, each of them serving as an impediment. If you’re the player who’s down, though, you have a ton of different shots to choose from, and your opponent so handily cleared the table of most of the obstacles in your way. In this way, the player currently losing has a competitive edge.
So, how should you build a comeback mechanic? Well, the first thing you need to think about is exactly what a “comeback” means, and what kind of comeback leads to the most enjoyable gameplay. Do you want your down-and-out players to have a moment of glory to level the playing field, like that provided by X-Factor, or do you want to simply slow the winner’s progress to give the loser a chance to catch up, like in pool? Do you want to make the winner perform a bit worse, like the blue shell, or do you want the loser to perform better, like the Bullet Bills also found in Mario Kart.
Another important consideration is that you don’t want winning players to per se feel like they’re being punished for being good, nor do you want people to feel like the optimal strategy is to lose (unless you do. If the strategy your game is trying to teach is “lay low until your time to shine”, a comeback mechanic might be a way to reinforce that). Generally, comeback mechanics aim not to create a route for victory, but simply to prevent getting absolutely facerolled. A comeback mechanic has still done its job if the loser still loses, but by much less than they would have without it. Better players should still beat worse players in the most common case, no matter how you slice it, but the comeback mechanic ensures that those worse players still have a chance to win at all.
I have a rough rule of thumb when it comes to comeback mechanics: the comeback mechanic should not, in itself, close the gap between a winner and a loser. After all, Mario Kart‘s Bullet Bill doesn’t take you all the way to first, and pool doesn’t let you just grab three of your balls and drop them in pockets if you’re behind. Instead, a comeback mechanic should be such that the comeback mechanic, plus some combination of player skill, opponent misplays, and luck can close the gap. That way, when a skilled player looks up to see that the opponent they were beating is now the winner, they know that, despite the comeback mechanic’s presence in the game, they still could have won, and when the losing player triggers the comeback mechanic, they have the challenge in front of them of using this opportunity to succeed.