Before starting the project, Buddies: Dash In Time, I had investigated many endless runners. Endless Runner genre is one of most popular choice within mobile casual games. In this article, I summarize the characteristics of this genre, and provide a simple classification. Endless runners can be classified into two sub-types: Horizontal and Vertical Endless Runners.
Horizontal Endless Runners
In this sub-type, there is a protagonist running on the left side of the screen and obstacles coming from the right side. For this reason, horizontal runners use landscape orientation on mobile screens to use the active area as much as possible.
Most popular examples in this sub-type are Canabalt and Jetpack Joyride, and their popularity is mostly due to their choice of minimalistic control scheme. (Hold/Touch to Anywhere). This is related to the structure of horizontal runner game sub-type which cannot integrate a complex interaction model. Majority of the horizontal runner games fail to build a game design that render four directional swipe useful. Most of them miss left or right swipe, or even both. In a horizontal oriented layout, lack of horizontal swipes is actually a big limitation. (Also, they fail to use gyroscope and accelerometer of mobile devices but it doesn’t form a big issue, as I’ll explain later on Vertical Endless Runners section). This is why swipe control schemes are less preferred in Horizontal Endless Runners. Games that don’t employ minimalistic control scheme usually use left/right action controls(hold/touch to left/right side of the screen have 2 different actions: one of them is always “jump”) rather than swipe control.
Another challenge for horizontal runners is left-to-right direction of the game. Since the obstacles come from the right side of the screen and the majority of people are right handed, even within minimalistic, touch anywhere control schemes, right hand obscures the player’s vision. Games with left/right action controls try to use the lower bottom part of the screen as dead (useless) space to ensure player’s fingers do not obscure the vision.
Another problematic aspect of horizontal runners is their lack of “Air Control”: with minimalistic or left/right action controls, one cannot direct the protagonist while on air. Since most of the platforming depends on jumping, lack of air control disturbs the learning curve. The reason for that is, on classical platformers, while on air, player can choose where to fall easily by using air control mechanisms, and users might confuse horizontal endless runner with classical platformers, for they look the same. This confusion brings a harsh learning curve and this can frustrate users easily. The most popular horizontal runner Jetpack Joyride clearly solves this problem by using no platformer elements and choosing a levitating protagonist rather than running & jumping one.
Last problem is, horizontal runners can’t be played by a single hand on mobile cell phones because of the horizontal orientation of the screen, even when they have a minimalistic, touch anywhere control scheme.
Vertical Endless Runners
In this sub-type, there is a protagonist running on the bottom and obstacles coming from the top, or, in most cases, a protagonist running in a 3D setting and obstacles coming from the depth. For this reason, vertical runners use vertical (portrait) orientation on mobile screens to make use of the active area as much as possible. Usually, 3D vertical runner games use a third person camera, and 2D vertical runner games use a top down or isometric perspective.
Majority of vertical runner games use tracks-lanes to organize obstacles and integrate four directional swipe control scheme. Player can change track/lane with horizontal swipes and jump/dive/crouch/roll with vertical swipes (Some of them could also use double tap for other actions to increase the depth of the gameplay).
Track/Lane counts vary, but usually minimum track number (three) is chosen. In general, if a runner have more than three tracks, it’s complexity increases and this can lead to a narrower target audience.
UPDATE: SYBO released a new vertical runner: Blades of Brim is a brilliant example of multi tracked runner game design, yet this decision directly limits the target audience to a more experienced fanbase when compared to their massive audience (1 billion downloaded) vertical runner game Subway Surfers. However, it should be noted that, Blades of Brim expanded the endless runner core game loop (with brilliant additions such as wall jumps and monster jumps) to a more advanced level, and this can bring new norms to endless runners, considering the audience’s increasing expectations from mobile casual games.
Some very polished and balanced games such as Temple Run, Temple Run 2, Traffic Racer and Minion Rush choose gyroscope as part of the control scheme. However, compared to Subway Surfers, we can see that gyroscope has a big negative role in the retention rates, possibly caused by its inconvenience to play in unsuitable places, such as metro, bus, or while waiting in line, etc.
In vertical runners, beginner gameplay rely mostly on changing track/lane actions and on simple jumps and rolls. Air control becomes more crucial for advanced gameplay with longer runs.
For 3D vertical runners, z-depth is very important in executing the actions on time. Usually this problem is handled by a cylindrical vertex shader that manipulates the world coordinates. (In technical respect, Curved World is a very good Unity 3D plugin that simulates the similar results.) This shader also hides the new generated upcoming map parts from player’s sight. The most popular game on this genre, Subway Surfers prefer to twist this shader to left. This decision greatly affects competence over depth for right handed players (It would be a better idea to have a left handed option on the settings). Also, fog has an important role in perceiving approaching obstacles’ z-depths.