Rocket Jump Mechanics for Side Scrolling Platform Games

Introduction

The revival of the platformer’s popularity in the recent years could be attributed to new breakthroughs in the area of game design. We have seen new and interesting game mechanics in Braid (2008) and Super Meat Boy (2010) that had breathed in new life into the genre. We can see that the platformer genre is reinterpreting game mechanics and design that was popularized in other game genres. For example, Braid’s idea of time manipulation was heavily influenced by other time manipulation games such as Prince of Persia: Sands of Time and Blinx (Totilo, 2007). Similarly, other mechanics like parachute jumping, or gliding have been used to inject more fun into platformers. Encouraged by these examples, we are looking to incorporate an existing game mechanic from another genre into the platformer.

Rocket Jump is a form of emergent gameplay that had gained popularity in First Person Shooters (FPS) like Quake (1996)Team Fortress 2 (2007). Rocket Jump was originally born from a game glitch that allowed the player wielding the rocket to be propelled across distance. The popularity of Rocket Jump was quickly noticed by many game developers and was subsequently incorporated as a core mechanic for many FPS games.

We are interested in applying the Rocket Jump as a novel movement mechanic for side scrolling platform games. In this game experiment, we compare the Rocket Jump mechanic with the conventional movement mechanics found in most platformers. Also, to aid in the design of the levels, we apply physics equations to the design of our game levels for the tweaking of level difficulty. The details of the Rocket Jump mechanic is discussed in conjunction with links to level design that afford balanced play and progressive difficulty, in a 2D side scrolling platform game. Throughout this process, we will be using the Mechanics, Dynamics and Aesthetics (MDA) framework (Hunicke, LeBlanc, & Zubek, 2004) as a design guide.

We first explore the underlying physical constraints of rocket propulsion (Mechanics). Following that, we create game levels that afford progressive difficulty (Dynamics). We feel that it is important to objectively visualize the challenge posed to the players even before user trials are done. Typically, level obstacle design is done manually by iteratively tweaking important variables and testing the resulting game-play. This approach has obvious limitations in addressing puzzles with many variables and different player skills but as a reference for a technical discussion of a mechanics implementation, we will not consider the design aspects of the mechanics. We describe a simple parabolic motion estimation framework that allows designers to calculate permissible ranges for successful jumps, and thus allowing them to create scalable difficulty without any guesswork. We suggest some values for key rocket mechanics and obstacle parameters for the reader’s reference and predict the corresponding game-play challenge. Besides evaluating the difficulty of the obstacles (Dynamics) by looking at the performance of the players, we also assess the difficulty of the Rocket Jump versus the Conventional Jump, to assess its pros and cons as a new mechanic replacing a well-accepted one.

This chapter guides the reader on how to design platformer levels to suit the Rocket Jump mechanic. The focus is not really on game design, but more on a practical framework for assessing difficulty and comparing the player experience.