In this project I will be producing a mobile game about a spaceship, visually styled like a modern day rocket, that travels forward in time and visits different civilisations from Earth’s history. I originally designed this game for the Apple Watch, however, I realised that it had more potential on a bigger screen where the spaceship and cities on the ground can be seen in full. I chose to pursue this game as my final project because I like the core movement of balancing moving up and down in the prototype (right). With some changes, which primarily involve allowing the player to change the acceleration of the spaceship instead of directly changing the velocity, I feel that this can be a fun movement system for a touchscreen.
I also like the module system where players can select modules throughout a run to change the gameplay, making things easier. This allows for different builds and playstyles, encouraging the player to customise their experience and experiment.
The game uses the theory of general relativity, that being how time flows slower for those in a gravitational field, to provide the player with an arcade-style game. In play, the player controls a spaceship that goes into space, after taking off from Earth. As the player escapes the gravitational field, by getting further away, time passes faster on the surface of Earth. The current year on Earth is always displayed at the top of the screen; this is also the player’s score value for their current run. The player can land on the surface, hundreds of years later, and encounter different civilisations throughout history. Each civilisation will be on the planet surface for a certain timeframe, for example, with the Roman Empire this would be between 600 BCE and 300 CE. The cycle of taking off and landing at different civilisations in time continues until the player inevitably dies.
The game is designed for mobile and can be played by holding down the screen to propel a spaceship into space, and letting go to make the rocket go back down. At its core, this is an endless runner that asks the player to continue playing and reach insanely high scores, or die trying. Death comes very quickly and players are prompted to retry, to see if they can beat their previous attempt. Because of this, the core minute-to-minute gameplay loop needs to be very engaging and ensure that the player wants to come back for more.
The core gameplay is about avoiding asteroids and collecting fuel pickups to keep using the spaceship’s thrusters; both of these fly in from the sides, as the player can only move up or down. Signals at the sides of the screen will indicate when one of these is coming, and where it is coming from, so the player can move accordingly. These items will come in waves, for example three asteroids across from the top right and two from the bottom left, that will be predetermined to create fun patterns for the player’s to predict and avoid. Players will eventually learn these patterns, become more skilled at the game and achieve higher scores.
The spaceship cannot take any hits and the player loses if they get hit by an asteroid. The player also loses if they run out of fuel, as they fall back down to Earth and crash. When going down, the player must regulate their downwards acceleration by repeatedly activating their thrusters in short bursts, otherwise they will hit the ground too fast and the player will lose. These are not initially communicated to the player, but they learn about them through each time they die.
There are, however, some affordances here and players will act according to them, for example, an asteroid hurtling towards the spaceship will suggest to most players to move out of the way. This will also be made clear in the signals that appear at the side of the screen, as for asteroids this will be a red explanation mark in a red triangle; this is the same as a caution symbol, suggesting something dangerous is coming.
To counteract the fatigue of constantly losing, there is an upgrade system that allows the player, whenever they land on the surface of the planet and encounter a new civilisation, to select a new module to add to their spaceship. This new module will drastically change the game, such as by making the spaceship’s thrusters fire in bursts or adding a rechargeable shield that protects against asteroids, and the player is encouraged to mix and match upgrades in each attempt.
The modules will give unique bonuses, according to the civilisation and time that they have come from. Whenever a player lands in a new civilisation, they are given a choice of 2 modules, specific to that civilisation. These two will be very different to each other, encouraging different playthroughs, as the player can only choose one. The player will also gain a small amount of fuel, enough to get them back to space, whenever they land on the planet surface. There is no other benefit to landing on the surface, during the same civilisations timeframe, as the player must wait for the next civilisation so that they can choose another module.
GIF demonstrating the player’s spaceship taking off from the planet’s surface, from modern day New York, and heading into space. As the ship flies upwards, the fuel inside it, represented by the yellow line, goes down
The spaceship will grow in size as more modules are added; however this makes the player an easier target for the asteroids. Players do not need to land on the surface and select a new module to add and, instead, may choose to stay in space to stay smaller. In this way, the game rewards different playstyles.
These modules can be upgraded in space stations at specific heights in space, for example, at 1000 metres up. This encourages players to reach these heights, which will make time even faster below and thus unlock new modules faster. However, the higher the player is, the more asteroids will appear and make gameplay harder. Once the space station is used it cannot be used again during that run. Players are therefore supposed to spend the upgrade on a module that they are focusing on for their build in that run.
I chose to include the module upgrade system so that I could still give the player options and allow them to improve their build during a run, whilst requiring less art to be produced. Each upgrade will only slightly change the visuals of that module, for example, a “Mk.2” may be written on it. Every module can be upgraded 3 times.
Developments in the rogue-like genre, in games such as Hades or Slay The Spire, have shown that it is helpful to have in-game bonuses accruing between the runs. These grow alongside player skill and still provide a sense of accomplishment to those who are having difficulty, as well as making the game slightly easier. For example, Slay The Spire has new cards unlock each time the player attempts a run, whether they die or win. In Propulsion I will add a similar mechanic, linked to the upgrade system, where a new space station will unlock every time the player gains a level between runs. Players will gain levels automatically between runs as their XP, which builds up to gain levels, will increase by the high score acquired in each run.
Outside of a run, the player can also unlock new skins by levelling up. There will be 3 skins available in the game: NASA, Russian, Chinese. Each of these comes with a unique colour scheme and design for the thrusters and cockpit of the spaceship; the colours of installed modules are the same as the colour scheme of the skin, but they may have an accent colour representing the civilisation that they came from. The game starts with the NASA skin already unlocked.
I have researched the general theory of relativity, having read Stephen Hawking’s A Brief History of Time and Robert Geroch’s General Relativity From A to B. However, my game is only based on the idea that time goes slower in a gravitational field but, whilst this is true and I feel that Propulsion explores the concept in a playful way, in reality the effect would be nowhere near as noticeable as the game makes it out to be. For this reason, I do not need to focus my research on the science any further.
I have also researched real rockets from different countries and explored how they differ. Rockets are also comprised of stages, which are similar to my modules, so I have researched these to inspire new modules, as well as their visual designs. I have put together images of both of these below.
