Achron Interview

20 Jan 2010 at 15:45:57 by Tim McDonald

If you've recently listened to our weekly podcast, you'll know that Tim McDonald has been spending some time with Achron, a real-time strategy game with a magnificent time-travel mechanic that allows players to hop backwards and forwards in time, potentially taking units with them. As Tim has difficulty understanding the concept of time barring "lunch," "later," and occasionally "deadlines," it seemed a good idea to have him chat with Chris Hazard, co-founder of Achron developer Hazardous Software.

If the interview tickles your fancy, pre-purchasing the game grants immediate access to the current alpha release of the game, as well as early access to further builds, mod tools, and more.

Tim McDonald: Being that time-travel in an RTS is a pretty wild concept, how did you initially come up with it?

Chris Hazard (right): I was up late talking to a friend about the RTS Homeworld a month or two after it was first released. We were talking about how it was one of the first RTS games to fully make use of the 3rd dimension for gameplay, and my friend asked, “what if someone made a 4D RTS?” My initial thoughts about a 4D RTS seemed interesting, but not novel enough that I'd want to pursue it. Then I thought about the possibility of adding time travel to an RTS; it seemed like the perfect genre for time travel, as you could do all the things you read about in science fiction about time travel warfare. I started working out the details, the core algorithms of how it might work, and talked to several other people about it. A few said it couldn't be done, which gave me the extra drive to pull it off. Based on my initial estimations, I reasoned that CPUs that people have at home wouldn't be fast enough for another seven or more years. I decided to start working on it and keep it secret just until the technology was ready and people had fast enough computers. Things came together last year and we unveiled at GDC's Experimental Gameplay Sessions.

What sort of problems did you initially have when trying to work time-travel in? I imagine the interface would've taken some work to stop players getting too confused.

Developing a game with free-form time travel was extremely difficult, and no one has ever done this before, so we didn't have much to go on. Time travel at this scale influences game design in subtle but significant ways. I could easily spend hours talking about all the unique problems we've solved with respect to gameplay and technology, but here are a few interesting examples.

Most RTS games have easy ways to group your units and issue commands to the group directly. However, if you can alter the past, you can assign unaffiliated units across the map to the same group, issue a command to that group, and drastically change the past relatively cheaply. Even seemingly small changes in the past can have large implications on the present and future like the infamous butterfly effect, where a butterfly flaps its wings, causes a rhino to sneeze, which causes a stampede, which alters the wind ever so slightly to direct a hurricane at North Carolina in the US. To prevent players from making the timeline too chaotic for opponents and to maintain balance, we implemented command hierarchies to keep players' changes to the past more locally contained. The player sets up a command structure, and then just needs to give the commander an order to control the hierarchy, which automatically sticks together spatially.

Another example is figuring out the timeline, which is an essential part of gameplay. It needs to convey to the player a map of the time and indicate what has happened, when the player should do things differently, and what opponents are changing. The tricky part was making sure that enough useful information is conveyed without being information overload. For example, although it is useful to see statistics of each of your resources throughout time, having a line for each would be visually overwhelming. Instead, we collapse resources into a single graph and use a variation on what is known as a geometric mean to combine them. This gives a result that is quite intuitive and informative.

The relationships between balance, freedom, and constraints are key components to achieving a fun game, and we had many unique design considerations. If a player were able to easily send resources through time, then doing so becomes a dominant strategy which isn't very fun to play. We've worked very hard to carefully tune the core gameplay mechanisms to give players freedom while keeping things interesting and competitive. As with any new strategy game, there are undoubtedly some balancing issues that will arise when we move into beta. However, I believe we have a solid foundation of gameplay that will allow us resolve any issues that arise to keep the game fun and balanced.

In terms of development, many techniques common to most game engines just do not work with time travel for performance reasons, so we've had to improvise across the board with respect to the design and algorithms in the game engine.

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