In Praxis… Traveling in time

In this installment of In Praxis I’m going to give a more in-depth technical overview of the main gameplay mechanic in Reset: time travel.

As shown in our gameplay tutorial video, using the mechanic is fairly simple: First you decide that you want to return to a particular point in space and time from the future. Then you do whatever you want to do and finally return to the marked point and moment. From that moment onward the previous version of you will be doing the same things you just did yourself, and you are free to do something else.

The way we have implemented this is to record the input from the player between the marking of the re-entry point and the reset. After jumping back we use the recorded inputs to drive a clone of the player character. From the point of view of the game engine it’s exactly as though there were a second player in the game.

As anyone familiar with time travel in science fiction knows, messing with history can have unforeseen consequences. The slightest disturbance of the previous timeline could set off a chain reaction of changes that result in a future unlike what you were expecting. This is a fundamental principle in chaos theory and is known as the butterfly effect.

One example of this can be seen in the gameplay tutorial video: the second time the hovertruck is moved across to the other platform, it ends up at a slightly different position. This is because that time the truck is heavier since there’s now a mech standing on it. We are still working on ways to artificially reduce the effects of small disturbances such as these, but ultimately you’ll have to be aware of how the appearance of a future you can change what you’ve done in the past.


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  • Comments (30)
    • Kein
    • November 12th, 2013 5:00pm

    I keep seeing comparison to Braid for some reason, but actually only Temporal game:
    matches Reset in gameplay mechanics pretty much 1:1.

    • Jochem
    • November 12th, 2013 6:05pm

    Will we be able to spawn more than one ‘past’ mech? E.g. set another ‘return point’ while the other mech is still working?

    • Yes, more complex puzzles involve more simultaneous timelines. It gets pretty wild. :)

        • Jochem
        • November 13th, 2013 5:37pm

        THAT’S AWESOME! :D

    • Timerider
    • November 13th, 2013 7:27am

    Reminds me of Chronotron.

    • Yeah, Reset lets you decide your return point in space and time though.

    • PrimatePriest
    • November 13th, 2013 12:18pm

    It reminds me a lot of “The Misadventures of P.B.Winterbottom” but in 3D. It’s a nice mechanic.

    Jochem :
    Will we be able to spawn more than one ‘past’ mech? E.g. set another ‘return point’ while the other mech is still working?

    I would like to know this too.

    • P.B is one of our inspirations. Yes, multiple timelines are used in more complex puzzles :)

  1. hm very interesting I must check it

    • urok
    • November 13th, 2013 11:29pm

    where can I get it ?

    • MikeVi
    • November 15th, 2013 5:02pm

    Brilliant design – so I’ve contributed and really looking forward to the release. I think your tutorial is an excellent indication of your uncluttered thinking. Don’t be tempted to give up when the going gets tough. This game deserves to see the light of day. All the best!

      • Mikko Kallinen
      • November 20th, 2013 12:48am

      Thanks! We’re glad to hear we’ve been able to convey that we know what we’re doing. :)

    • Balázs Török
    • November 17th, 2013 11:09am

    Very interesting video and article, our team has been trying to fix these problems for a while with input recording. Can I ask what you are doing to avoid problems with the frame time differences? Also do you use multithreading in the gameplay? If yes then how do you deal with that? Do you store anything else than the user input (like the player positions) to fix the divergencies? How long is the maximum capture that you support?

    If you would be interested in a more in depth conversation, you can email me any time.

    Wish you the best on your campaign!

      • Mikko Kallinen
      • November 20th, 2013 12:46am

      Thanks! We run the game logic and physics at a fixed rate. Also currently only the physics simulation is multithreaded and behaves in a very deterministic fashion. Right now we only store user input and even in its unoptimized state it only consumes about 1 kB/s. Even an hour of recording only takes about 3.5 MB. We will probably have stricter limits than that by design.

    • Domovik
    • November 19th, 2013 5:46pm

    What programming language did you use to program the PRAXIS engine?
    Maybe Python or C?

      • Mikko Kallinen
      • November 20th, 2013 12:38am


    • Steven_RW
    • January 29th, 2014 4:11pm

    This game looks awesome. Loving following the dev. I supported the kickstarter campaingn and, whilst I admit a terrible memory at times, I don’t recall which video was used for the kickstarter campaign. Was it the HD trailer or something else? If so, can I still watch the original?

    Keep up the hard work everyone :-)


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