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F.R.O.G.: Developing a Physics-Based Sandbox

Elijah Horner, one of the developers behind F.R.O.G., talked about their indie title that features a cute frog with a shootable tongue: physics, world creation, character, and animation. You can back the project on Kickstarter.


My name is Elijah Horner, I was born and raised in Abbotsford, British Columbia.  In May of 2018, I attended Vancouver Film School (VFS) Game Design Program, where I met 4 other individuals who all shared a passion to create quirky games, and that’s how Team Primitive was formed!

From left to right: Nathan Krelekamp (Level Designer), Tyler Vermeer (Systems/Mechanics Designer), Alberto Buitrago (Artist), Elijah Horner (Project Manager), Justin Kwiatkowski (Programmer)


F.R.O.G. was made inside the Unity Engine, and the idea for F.R.O.G. was born from the team wanting two main things:  1) a cute lovable character who anyone can fall in love with, similar to Sly Cooper or Mario 2) a simple mechanic that anyone can master, similar to Portal. From that our character, Todd Pohl, was formed! He’s a cute Red-Eyed Tree Frog that everyone thinks is cute, and also has one main mechanic which in the shootable tongue!  Once we had the core idea of what we wanted the player to be playing as we designed a game around the mechanic, making sure that this one mechanic we picked would be usable in every situation.


The main physics system we have inside F.R.O.G. is the tongue and how it interacts with things in the environment. The tongue is made up of little balls that are all being connected by spring joints and hinge joints to give them the flexible range they have, as well as add a bit of “stretchiness” to the tongue.  The major challenges came into play when we started having the tongue interact with other physics objects: we often had the tongue explode on us because the springs and hinges couldn’t handle what we were throwing at it. But our programmer who spent a majority of development on the tongue continued to tweak and change it to what we have now, which шы a much more stable version, while still keeping wacky physics fun!

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Our development cycle for creating assets was definitely unusual. Quite often we would get people to play our game in whatever current state it was and let them ask for items. We would then sit down as a team and discuss if that item could somehow benefit gameplay, without having to change our mechanics. If yes then we would have a prototype working while our artist would create it using Maya and Substance Painter. Most of our assets were very “spur of the moment” things, but that’s because we had a team that can create those types of assets very quick. There wasn’t anything too challenging to create, the overall challenge was ерфе a lot of assets were quick ideas and often were time-crunched.

World Creation

When we were creating our worlds at the beginning, this game was very linear. It was meant to be a “complete one challenge go to the next one”. While we were working on those levels though, people had more fun just messing around and doing the challenges. So as a team we changed our level design up to still include those challenges that we have worked on, but give players more choice to go play and have fun if they choose to. The hardest part about designing any game is letting go of something you have worked on, it was definitely a challenge to let our levels go and start somewhere new. But in the end, it would benefit the player, and the player comes first.

While laying out the challenges in our new world, we wanted to set them up in a way that encourages the players to explore. So some of the challenges can say “go find all 10 crayons”: the player knows that it is a challenge, but then may explore any cool looking area out of the way and either find that crayon, or a new fun experience. Or when completing a certain challenge they might end in a different section of the map, a place they haven’t explored yet.


The character itself is arguably the core of our game. His name is Todd Pohl, – again, we tried to get that cute name to match a cute character!  All animation was done by our artist and everything was hand-animated using Maya. The tongue is done slightly different: it basically has an “Anchor” placed in the back of the mouth, so when the head is bobbing up and down, the tongue will stay attached and won’t clip through the frog’s head. Knowing this, our artist made sure to make all the animations with Todd’s mouth open, so he never needed to make a “Shooting” animation – the tongue just flies out. The tongue is also always there, but when it is retracted all the way it goes invisible, so the player doesn’t see it.

The ragdoll effect is all just physics. There is no animation needed for falling over or getting up. Being a frog, Todd’s get-up motion was easy – we just made him jump up in the air and played our falling animation as he landed.

Future Plans

Our next goal is to create more levels that can still challenge the use of the tongue. We are very open to different themes and structures of levels, but the tongue mechanic comes first and will always be considered when making a design decision. We have also talked about co-op or multiplayer, there are no promises right now, but it is something we are looking into.

Elijah Horner, Project Manager

Interview conducted by Kirill Tokarev

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