State of Flow: Plants vs. Zombies
When I think of the “golden era” of mobile gaming I think of many games which now may be considered as classics. Among such games as Flappy Bird, Angry Birds, and Doodle Jump, one stands near the top. Plants vs. Zombies took every single person with a smart phone by storm. This cartoonish tower defense game became popular enough to warrant many sequels even in other genres. Of course, the idea of plants defending against zombie hordes is a novel idea and may draw player attention at first. However, players usually do not stay and lose track of time based on concept alone. Plants vs. Zombies is a game where I found myself playing during down time and saying to myself “One more round”. The reason for this achievement by this game like many other “classic” mobile games is its successful design in terms of inducing a state of flow.
When players first began this game, many were new to the genre due to the sheer accessibility of a free game at the start of the smart phone era. As new players begin the game, it seems quite simplistic and straight forward. At first the game runs the player through a simple tutorial where they must plant shooters on a single grass lane, and tap sun drops to keep planting. Once they are successful, zombies begin to walk one by one to introduce the core idea of the game. Once nearing the end of the level, the player is warned about a huge horde incoming that they must defend against. Once the player kills the horde of 2 or 3 zombies, they are rewarded with the sunflower unlock. Looking at this tutorial level and how it leads to the next, we can easily see the formula used in this game to induce a state of flow.
Firstly, we can see the level itself raised in difficulty with zombies attacking at shorter frequencies until the difficulty reached its climax at the end of the level with the zombie horde. This formula is kept through out all levels to induce a state of flow within each level. Once the level ends, the player receives a new plant adding complexity and choices to the game to raise difficulty and keep player interest. At the start of the next round, the game always starts at a lower difficulty than the horde from the previous level and ends with a horde of its own which is stronger than the previous. Through this design pattern, Plants vs. Zombies keeps an ideal shape on the interest curve for each level. On top of this each level introduces change in terms of level design.
As the player progresses, each level evolves with the players skills. With each level the yard itself is changed to introduce more complexity. At first the player is introduced to more lanes they must protect. Slowly, the yard begins to vary even more by including such things as pools. Through these changes, the player is forced to constantly tweak their strategy to adapt to the level design itself. In this regard, Plants vs. Zombies induces an effective state of flow.
With each change in level design, the enemies also change. As the player begins building their strategies the game introduces different zombie variants that may counter specific plant types while being weak to others. New mechanics such as blocking zombies, zombies that may jump blockades and zombies who may push plants are introduced as the player progresses. This concept of new enemy variants is used to scale difficulty as the player begins to feel comfortable defending against zombies with their plants.
With all these changes, the game builds a few systems to assist the player in learning and evolving with the game. The most obvious systems are the tutorial and information systems. With these the player sees tips and information on plants and basic mechanics which lead to basic dynamics such as planting sunflowers behind shooters. Slowly the player evolves past these and builds on the existing dynamics. Another prominent system is the level itself. With each level, the player is introduced to new zombie variants and the level design changes and must find the best method of defense. The level always starts relatively slow and builds speed and difficulty to ensure the player has enough time to learn. Then the player is tested once the horde is unleashed with the same enemy variants the player has seen before. This introduces the need of both planning and in the moment decision making. One final system is the lawn mowers at the end of each lane in the yard. If a player fails to defend a lane in the yard, they are given a second chance to deploy what they have learned as the lawn mower clears the lane.
Through these systems and its progression in and between levels, Plants vs. Zombies manages to induce a rather successful state of flow. As the player starts looking at one lane of grass and a handful of zombies their interest is peaked. The game ensures that without even realizing it the player progresses to still be challenged while fighting off athletic zombies with a plethora of plants in a mad tapping frenzy. Who could have thought the most effective way of preparing for the zombie apocalypse was yard work?
