‘Zombie Rescue Squad’ is a casual run-and-gun cooperative shooter made for the Snapchat Games platform. I was the Lead Designer for the project from start to finish.

CONCEPT

Snapchat had come to PikPok asking to develop a game for their new gaming platform. As the platform focused on playing with friends, we pitched ‘Zombie Rescue Squad’.

ZRS is a top-down coop-etition shooter where you must jump out of a Helicopter, rush through a stage, save civilians, and get to the end, while keeping your squad mates alive.

The game was built on Snapchat’s PlayCanvas - an online development tool which was purchased to develop games on their platform - no Unity, no Unreal - all PlayCanvas.

To simplify the requirements for online pings, the game uses a grid system for movement. This way we could just send where the character needs to go, and not every single detail of the movement.

All Zombies are locally positioned, but follow ‘Agents’ (red dots), which simplifies the packets sent online.

We didn’t want to make the game dual weilding - it felt too hardcore and vertical games with dual sticks feel odd. To keep the fast pace, we made you auto aim. You ALWAYS want to shoot Zombies, so focus on not getting eaten.

STAGE BUILDING

We wanted to have a system in the game to build stages easily, but also be randomized. Being on a system like PlayCanvas meant we had to be creative.

Stages are built on 32x32 tiles, in which their collision is based on the grid spaces, and are exported to JSON. Each has a beginning and end section - as long as those sections stay the same, any stage can connect together. With 3 stage styled (Metro, Park and Concrete) we built 300 tiles, which can be placed in 90 different layouts. A layout can request a Metro Up tile, which begins and ends at the bottom and top, and there are 8 of these.

Therefore, there are roughly 930,937,679 different stages that can be played through.

Each tile has a specific start and end. as long as those are clear and the player can go through them, anything else can happen between them.

Tiles are turned on when they appear in view to keep the draw calls low. Zombies also only spawn when you are close enough to them being able to spawn. This keeps everything low cost for a mobile game.

We built 300 tiles for each type - corners, south to north, the lot.

This results in a massive amount of levels that can be developed. A new experience with every playthrough!

Over 90 layouts were also created, which would be used across each type of tile. The end is always at the top of the stage, keeping things simple for the player.

And the result looks like this. Seemless!

BALANCING

Being on Snapchat and very casual, we needed to allow players to jump in at any time. This meant we needed to solve the balancing issue.

In the game, each player has a rank - which determines the weapons they have and the types of Zombies. While in the game, the Average Rank of all players determines the types of Zombies available. In addition, more players means more Zombies also spawn. This then rebalances based on the Zombie spawn trigger - so if a player jumps in or out, it will rebalance.

The game has a score - harder Zombies are worth more, and all points go towards XP. If a player was Rank 1 and another Rank 10, the the Rank 10 player would get less points, but would mean the Rank 1 player would get more - boosting them up!

Bonus rewards are also given at the end of a run - and more are available with more players playing.

This might make the game a bit easy, but focuses on having more fun, fast.

MONETIZATION

On the Snapchat platform, the game only had ads as part of monetization. Originally these were 30 second ads that were unskippable and required you to request an ad and not be forced to watch one.This has since changed to be shorter and skippable.

Based on this we designed to have these ads be outside of the core game - you could get a boost before a match, or double your rewards. When you had enough to upgrade a weapon, you would also watch a video.

Watch an ad to get a boost at the start of the game, such as being invincible for 30 seconds, or doubling your points.

After finishing a stage, you can double your rewards.