Game Design Document

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Surge the Rabbit™ is a free and open-source 2D retro platformer inspired by Sonic games. It creates the experience of joy with its gameplay, graphics, sounds and level design featuring a style from the 90's.

  • Basic intent: create a fun, child-like and compelling gameplay experience.
  • Target audience: children, teenagers, young adults, people who were children in the 90's.
  • Target hardware: desktop computers and mobile devices (multi-platform). It's available in all platforms that run the Open Surge Engine.

This document briefly describes the main elements of the game.


Surge the Rabbit is played similarly to the Sonic games of the SEGA Genesis.

  • Controls: players use directional controls, as well as an action button, to control Surge and his friends. The action button usually makes the characters jump. However, different characters have different special abilities. Those abilities are triggered by a character-dependent combination of the directional controls with the action button. On desktop computers, players can use the keyboard and/or a joypad to control the characters. On mobile devices, a virtual joypad is displayed on the touch-screen.
  • Goal: the goal is to get through the levels, which come in a predefined sequence. Levels are divided in 3 zones each. Getting through levels means getting to the "end" of each of their zones. This usually happens by turning a goal flag (zones 1 and 2) or by breaking a goal capsule (zone 3).
  • Physics: the game has very similar physics compared to classic Sonic games, albeit the implementation is completely new and free (meaning: free and open-source software).
    • Abilities: walking, running, jumping and rolling are abilities that are common to all playable characters. Additional abilities are posessed by different playable characters.
  • Levels: zones have a beginning (a point in space in which the playable characters are spawned when first entering a zone) and an end (a point in space in which a goal sign or a goal capsule is located). Players get through numerous challenges and can use multiple routes to clear the levels.
    • Gimmicks: levels are rich with creative gimmicks, which are items that enhance gameplay in fun and original ways. Gimmicks are divided in two types: level-specific and generic. Level-specific gimmicks appear in a single level and are in line with its theme. Generic gimmicks appear in multiple levels and are not tied to a particular theme. Generic gimmicks are also called generic items.
    • Baddies: non-playable characters that appear throughout the levels and represent a challenge to the player. The player can take damage from them. Baddies are usually, but not always, beaten by jumping or by rolling on them. Different levels have different baddies with their own unique behaviors.
    • Traps: traps also represent a challenge to the player, but unlike the baddies, traps are not characters. Traps appear in obvious ways such as spikes, or in non-obvious ways such as challenging sections of the level design.
    • Bosses: the player fights a different boss at the end of zone 3 of all levels. Easier "sub-bosses" also appear in some particular zones.
  • Powerups: the player can collect different powerups to get a temporary boost related to power, ability or protection.
    • Invincibility: the player will be invincible during 20 seconds. When invincible, the player cannot take damage from baddies. Instead, baddies are instantly defeated on collision. Bosses take damage on collision.
    • Turbocharge: the player will be able to move faster than normal during 20 seconds. Turbocharging is meant to be used in sections of the level design in which the player is expected to run - never in platforming-intensive areas.
    • Shields: shields protect the player from damage. Some of them grant additional special abilities to the players (more on them below).
    • Super mode: when in Super mode, players become invincible. The Super mode consumes power at a rate equivalent to 1 battery per second. When no power is left, the Super mode ceases to be and the player returns to normal. Players can become Super by opening all magical wheels of power (see the plot) and by having power equivalent to at least one lucky bonus (see below).
  • Player stats:
    • Power: power protects the player from damage. It's represented by collectible batteries (see below).
    • Lives: players start the game with 5 lives. During gameplay they can win extra lives, as well as lose existing lives. If the player loses all of its lives, a "game over" animation is displayed. In this case, the player is given a new opportunity to start over from zone 1 of the same level.
    • Score: a score counter.
  • Underwater: some levels have underwater sections. When underwater, players move at a slower pace. Players need to breathe and can remain underwater up to 30 seconds without taking a breath (after this time, they lose a life). Players can breathe by using an underwater bubble, by being protected by a water shield, or by getting out of the water.

See also: Level Design Document

Game engine

Surge the Rabbit is powered by the Open Surge Engine: a powerful and flexible open-source game engine with built-in physics, level editor, scripting support, and more.

Main article: Introduction to Modding


Surge the Rabbit features beautiful pixel art with lighting and shading, which creates a retro atmosphere of the 90's. The music and the sound effects contribute to and enhance that atmosphere.

Main article: Art Specification Document


Surge was playing video-games and streaming his virtual adventures to his fans online. Even though he considered his day-to-day life to be happy, he always wondered if there was something more to life. His virtual adventures were exciting, but he wondered if he would ever live some adventure that was real.

Being an avid reader online, Surge came across a strange story about a global takeover orchestrated by hidden, dark magical powers. According to that story, there was a plan to takeover the world and imprison its inhabitants. The intent was to reset the world and turn it into a world ruled by dark magic. That plan was going on for years, mostly unnoticed by the people, and "they" - the hidden powers - were about to launch a major magical attack to grab power over the entire world and its population. Most people dismissed the story. Some even laughed at it. Surge, on the other hand, sensed that something was indeed going on, even though he couldn't put his finger on it. Something was not quite right in the psychic "atmosphere".

On a certain night, after streaming for several hours, Surge went to bed. He received a dream with a message that confirmed his suspicions. In the dream, he was told that dark magical powers had indeed been infiltrating the hearts and the minds of the inhabitants of the world for many years, and that soon their bodies would begin to shift due to the influence of dark magic. That dark magic could only continue to advance if the inhabitants of the world remained "asleep" to its operation - as they had been. He was told that if he opened the seven magical wheels of power, there would be a boom of light - and then darkness would be no more. He was advised to go to a place called Sunshine Paradise. There, he would find tangible evidence of innocent creatures being transformed due to the influence of dark magic.

Upon waking up from the dream, Surge was thunderstruck. Even though he didn't fully understand it, the dream seemed so real to him, unlike any other dream he has ever had. "Sunshine Paradise?" - he asked himself. "I have already heard about that place. It's not far from where I am". He decided to go to that place and check things for himself. Maybe that was the adventure he always wanted to live.


Surge the Rabbit

Surge is a charismatic rabbit who loves to play video-games. He helps to put an end to the works of dark magic.

Main article: Surge the Rabbit

Gimacian the Dark

Gimacian is an evil wizard who wants to transform the world into pure darkness and become its absolute ruler. He's the mastermind behind the global takeover.

Main article: Gimacian the Dark


Main levels

  1. Sunshine Paradise - a bright, cheerful, grasslands level with innocent creatures.
  2. Waterworks Zone - an industrial level located on a massive dam.
  3. Amazon Temple - ancient ruins and secrets hidden in a deep jungle. It's filled with hang-gliders, but winds are sometimes erratic.
  4. Music Stadium - a dream-like place that seems out of this world. Music notes are everywhere.
  5. City Chill Zone - a city covered in ice due to Gimacian's powers.
  6. Dragon Zone - a sand level that is the habitat of dangerous dragons and legendary creatures.
  7. Magma Fortress - a fire level filled with burning creatures possessed by Gimacian.
  8. Gimacian's Lair - final battle, single zone. A dark place hidden within Magma Fortress.

Bonus levels

Pseudo 3D levels in which the player can open the magical wheels. Different dimension.



This is a list of generic items that are not specific to any particular level:

  • Batteries: collectible items that represent power. They protect the player from damage. If the player gets hit, power is lost. If the player gets hit without having any power, a life is lost. On the other hand, if the player manages to collect 100 batteries (or any multiple of 100 batteries), an extra life is won.
  • Shields: shields grant additional protection to the player. They are obtained by smashing certain types of item boxes. Some shields also grant additional abilities to the player.
    • Normal shield: a shield with protective purposes only
    • Thunder shield: a shield that attracts batteries that are nearby the player
    • Water shield: a shield that lets the player breathe when underwater
    • Fire shield: -
    • Wind shield: -
    • Acid shield: - drop? repurpose?
  • Item boxes: they are spread throughout the levels and symbolize powerups.
    • Extra life: grants an extra life
    • Extra batteries: grants 10 batteries
    • Lucky bonus: grants 50 batteries
    • Invincibility: enables the invincibility mode
    • Turbocharge: enables the turbocharged mode
    • Normal shield: grants a normal shield
    • Thunder shield: grants a thunder shield
    • Water shield: grants a water shield
    • Fire shield: grants a fire shield
    • Wind shield: grants a wind shield
    • Acid shield: grants an acid shield
    • Trap: damages the player when smashed
  • Switches: they trigger some event when pressed
  • Checkpoints: once touched, they change the spawn point of the player in the zone
  • Goal sign: a sign placed at the end of the zones. The zone is cleared as soon as a goal sign is touched.
  • Goal capsule: a capsule that appears after defeating a boss. The level is cleared as soon as a goal capsule is broken.
  • Spring pads: spring pads propel the player in different ways.
    • they come in eight directions (N, NE, E, SE, S, SW, W, NW)
    • they come in three different strengths (normal, strong, stronger)
  • Bumpers: makes the player bounce back upon collision.
  • Spikes: objects spread throughout the levels that challenge the player by causing damage when touched.
  • Zipline: helps the player go through areas with high speeds.
  • Pipes: makes the player travel through complex systems of pipes.

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