Leading Design Challenges
Last Friday’s post Inspiring Design has provided some initial direction for game design. I concluded that the concepts of intuitive crafting, design gameplay, and spaceship simulation inspire me. This allows us to start conceptualising a game that incorporates these concepts, and finding the design problems in these concepts which need to be at the front of the queue. I will start by discussing two styles of gameplay found in existing games, and then talk through two issues which make combining these styles difficult.
It is easy to divide games set in space into two categories, games that play out within space vessels, which themselves are fairly static, and games that concern moving spaceships around, without much going on inside. Some interior focused games such as Faster Than Light and Heat Signature join Space Station 13, whilst the exterior focused Children of a dead Earth sits alongside Kerbal Space Program. Most of these games contain both flavours of gameplay, but the link between them is often only cursory. In playing many of these titles I have wondered why the spaceships are so happy to ignore us mucking around inside them, or why we’re so keen to blaze around the solar system with nothing to do when we get there. There are two barriers between these different gameplay styles that go someway to explaining the divide.
Varied time scales
The first obstacle to merging these gameplay styles is a large difference in time scales. We expect to move around inside ships in more or less real time, yet orbital manoeuvres can take months or years. Whilst we might just try to accelerate any ship level gameplay components, this compresses the length of any interesting situations for the interior gameplay, namely interior interactions between ships, trading, boarding, mining and so forth. The two solutions seen in other games boil down to either leaving out one of these gameplay types, or allowing players to control how quickly time passes in the game. The player might want to have a fight in real time, and then fast forward through the journey afterwards. The disparity of different passages of time is jarring in a multiplayer context. There are potential issues if different players have different passages of time near each other. The game could be segmented into levels, which ships simply teleport in between, but this curtails any exterior focused gameplay, as the ships would only need to be flown out to a level exit, rather than between stars. Thus a system bridging the different time scales would be ideal. As a feature of the game this would be simple, but potentially a feature of the game world, such as some non existent technology, would be able to bring orbital and interior time scales into parity.
Relativistic time dilation
This manoeuvre is gonna cost us fifty one years!
Being so explicit with the problems posed by time advancing at different speeds brings Christopher Nolan’s film Interstellar to mind. In the film, the necessity of passing deep into the gravity well of a black hole causes time to pass much faster on a ship than for the rest of humanity. This effect of gravity on time is entirely accurate, though where for the characters of the film the effect is significant, in our lives it goes unnoticed. For the design of this game, gravitational time dilation might provide in game machinery to balance different time scales.
The two effects on time dilation are easy enough to state. Accelerating to a high speed makes time pass slower than where you left, as governed by special relativity. Moving down a gravity well towards a large mass like a black hole makes time pass faster than where you left, as governed by general relativity. If we assume we’re in orbit around a black hole, spinning quickly around it rather than just falling in, then our orbit will have to get faster the closer we get. This pits the time dilations of special and general relativity against each other. To see if the time dilation could be useful for the game, we want to know what difference in timescales is possible, and how hard it would be to move between them.
To start with, we know we’ll want to be in a stable circular orbit around a black hole. To orbit neatly near a black hole means we’ll need the black hole to be spinning really fast along side us, so we’ll say that it is. To get really near a black hole without worrying about spaghettification means the black hole has to be supermassive, so we’ll say our black hole is one million times as heavy as the sun. Knowing the mass of the black hole we can start to talk about some of the orbits that are possible around it, and the time implications of moving between them. Say we’re in the smallest spaceship we can think of, perhaps it’s three meters across, and we want to orbit as close as possible to the black hole, with a tiny safety margin. The closest possible orbits to the black hole approach what’s called the photon sphere, which is the last orbit possible even for light, and half as far again from the event horizon surface as that horizon is from the middle of the black hole. If we keep the ship fifty centimetres from the sphere, that puts the centre of our tiny ship two meters from the sphere. We can work out that the photon sphere of our supermassive black hole is 4.43*10^9 meters from the middle of the singularity, and our mass is two meters further out. To hold our orbit, we need to be travelling at two hundred thousand kilometres a second, or 0.71 of the speed of light. This is as high as time dilation is going to get, with events unfolding thousands of times faster than back on earth.
There is a problem with this. Whilst time on this ship is going pretty slowly, the only ships near it are going to be similarly slowed. In order to actually feel time dilation in the context of a game, we need to find high relative time dilation. We can speed time up by extending into an orbit further from the photon sphere. Solving the equation for the radius of the orbit with time fifty fold faster than that of our slow time orbit, we can find a second orbit five kilometres further from the black hole, travelling 179 meters per second slower. The time decay as we approach the photon orbit is asymptotic, so an orbit twenty five times faster is only one kilometre away, or an orbit ten times faster just two hundred meters. This band about the photon sphere, between two meters and five kilometres, is perfect. The interior actions take place in real time, nearer the black hole, whilst ships can break away into accelerated time to travel between sites.
Does this black hole idea bring much to the game itself? Ultimately this is contextual flavour, and does not directly impact gameplay. Despite this, we have an immersive setting which conveniently lends a robust time acceleration mechanic within the game’s universe. If time acceleration becomes a regular element of gameplay it can be executed entirely in context, without having to acknowledge the fourth wall. We also generate some specific details for the setting of the game, with civilisation already in the most extreme possible orbits of a supermassive black hole. Finally, this would dictate that the spaceships of the game world all need to be designed flat. In a game explicitly planned to be two dimensional, this provides an explanation conspicuous in its absence from many games!
Different simulated foundations
The second impediment to bridging interior and orbital spaceship gameplay is between the two spatial styles. Games with an interior focus tend to play as games. We might expect a character to enter a fairly static level, and move themselves around intelligently at the behest of the player. In contrast games with exterior focuses tend to simulate the results of lower level instructions. Rather than clicking on another planet, we instead have to point our ship in the right direction, and fire our rocket engines. These two control schemes make a lot of sense respectively, but they do not naturally mesh. We would not want to walk around a spaceship clicking one foot at a time, and similarly we would not want the our spaceships to fly automatically. In order to blend these styles, I will try to develop a method of simulating spaceships that is appropriate both for orbital manoeuvres and interior gameplay.
The next post on Monday will introduce a prototype physics simulation aiming to address this divide.
