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The Constraint Histories of Digital Games

Drop7 and Volatility in Puzzle Games

drop7 During one of the talks at DiGRA, the person sat in front of me seemed far more intent upon the puzzle game he was playing on his iPad than he was in the talk – although he asked perfectly cogent questions afterwards. Later that day, another delegate showed me the same game – Drop7, now owned by Zynga – and discussing what had happened earlier we discovered it was Eric Zimmerman who’d been playing it in the session. He said it helped him to concentrate, and asked if I thought it rude to play in the talk. I pointed out half the delegates were typing notes or tweeting from their phones, so it scarcely mattered. But I became interested in this game that he'd used as an aid to concentration. What made Drop7 tick?

The essential play of Drop7 draws from the well established tile-stacking genre that flowers from Tetris. Whereas Pajitov’s classic relies on the simplicity of it's mechanics for its appeal (anyone can work out how to stack tetronimos), later tile-stackers such as Dr. Mario, Super Puzzle Fighter, Baku Baku Animal and Puyo Pop focus on combos to drive interest. The player learns to stack tiles in such a way that, when correctly prepared and then triggered, a giant chain reaction occurs. This reaction is the core of Drop7’s appeal as well, but unlike earlier stacking games Drop7 has a secret weapon in its rules.

Failure in tile stacking games occurs when the board becomes stable, which results from a configuration where the reactive combinations of tiles cannot be made to come into contact e.g. in Super Puzzle Fighter, tiles of the same colour don't touch. Conversely, it is possible to stack tiles chaotically in such a way that a small landslide will trigger large (accidental) chain reactions. This quality, volatility plays almost no role in Tetris but has been core to all other tile-stackers since.

Ordinarily, the volatility of any given board is a function of spatial dynamics – reactive sequences must be close to one another, yet incomplete. In Drop7, however, reactions are not triggered spatially but on a tile-by-tile basis. The rules of Drop7 (unusually) state that tiles react based on their individual horizontal and vertical line counts. This creates unique play options: a tile at the base of a stack can be triggered by action elsewhere on the board, whereas the traditional tile-stacker requires an open channel to trigger reactions by direct proximity. A side effect of the per tile reaction paradigm is increased volatility in practically every configuration – Drop7 boards become stable only as low-numbered tiles form a crust above locked tiles.

The locked tiles are key to making the game work. Expert players can position the locked, blank tiles to sustain future chains, but perhaps more significantly each locked tile has a high chance of reacting when it is revealed. There is, crudely speaking, two 1 in 7 chances for each newly revealed tile to react (randomly matching the horizontal or vertical tile counts), meaning each has more than a 1 in 4 chance of such a tile reacting wherever it is revealed on the board. This ensures highly volatile boards. Although previous tile stacking games have occasionally featured locked tiles, the spatial configurations required for reacting made these tiles contributed stability not volatility to the board. In Drop7, these blank tiles are more volatile than any previous game of this style and this adds significantly to the appeal.

Although there is some strategy in Drop7, the game’s compulsive play is rooted in fooling the player into believing they are critical to the outcome of each board (when dispassionate analysis would suggest chance was playing a major role). Key to this is the near miss effect, which causes a release of dopamine (as if winning) when players nearly win, motivating persistence. As with all good tile stackers, most players finish every game with the compelling sense that they could do much better next time, despite success being highly contingent upon luck. The near miss effect is associated with gambling, but is generated strongly by any game with a high role for chance, including tile-stackers, and tile-matchers, like Bejeweled. In all these cases, a high element of luck means even an incompetent player can do well sometimes, while high volatility makes for a more exciting and rewarding game.

Drop7’s design has a few issues, particularly in terms of game length. A competent player can play one game for more than an hour, which is rather long for any tile-based game – especially when the near miss effect is encouraging players to have ‘just one more try’. Having a marathon mode (called ‘Normal’ in Drop7) usually means having a sprint or blitz mode as well, but none is currently offered. This leads to more than a few people having to give up the game because there’s no ‘safe’ way to play it. (I myself deleted it two weeks after downloading it, and not from boredom).

From the accessible simplicity of Tetris, the puzzle game genre became stuck in a rut of tile-stackers based largely on colour matching and time pressure. Bejewelled kept the coloured tile matching but sidelined the arcade-style time pressure as optional and ditched stacking in favour of high volatility boards that automatically restock. Drop7 attains similarly volatile boards with more classic stacking play made interesting by a new approach – per tile conditions instead of spatial conditions. Note also that time pressure, now wholly unnecessary, has gone from optional to entirely absent.

Success for puzzle games lies in the combination of simplicity and volatility, and Drop7 enjoys the benefit of both, delivered with clean lines into a compulsive screen-tapping repetitiveness that easily becomes hypnotic. That focused so-called ‘flow’ state is easily reached by tile games (and solitaire card games), a stream of dopamine-releasing decisions that absorbs attention coupled with near misses to drive repeat play. But to keep the player’s attention, the game must offer, in Sid Meier’s memorable phrase, interesting decisions – or at least, interesting outcomes – and in tile games, it is often volatility that provides that interest.


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