A co-op level with difficult dexterity
You can have harder levels in co-op. Initially, the levels in co-op and single-player were the same, and therefore the benefit to bringing a friend is that you can solve the levels faster with more minds/thumbs. However, when I decided to have entirely separate levels for co-op, I noticed that not only did you have more minds, but a greater chance of one of the team members saying "one more time" on a particularly difficult level. The progression through that level felt faster as well because there was less of a chance of getting stuck down one rabbit hole since each mind on the team worked differently. Ultimately, I made those levels more difficult because I felt that I could, and I'm a bastard like that.
Know Your Role
When I first watched groups of people play the game it became clear that everyone couldn't be the puzzle solver. Nowhere was this more evident than in the first level. I originally had the same levels for both single player and multiplayer, and the first level was a simple straight line with one circuit piece turned the wrong way. Every player would rush toward the piece to turn and collide with one another. While it was absolutely hilarious to watch the TOM's all bounce off one another, get their angry face on, and curse at one another, it was clear that that would only be amusing for a few levels. Eventually I needed to solve the problem of everyone trying to solve the lead edge of the infection by turning the next piece.
One of the ways we did this was with roles. I momentarily debated giving different TOMs different abilities like classes. I didn't like this because I'd be asking people to choose a class based off no prior knowledge (In an FPS you'd have context for what a "sniper" character would be, but there weren't many class based puzzle games), and I also wanted people to be able to dynamically shift their roles based on the need. So what we did was give all of the TOMs various skills, and then put players in a pressure cooker, where they couldn't win if they all did the same thing.
I also believe in attacking a problem in multiple ways, so in addition to making it necessary for players to take on various roles, we added what we called a "role results screen" where players got awards for being the best, or worst at a particular role. This not only underscored the idea for players to take on different roles, but added a slice of competition, and even some mocking for players that weren't pulling their weight. We tried to make the award icons a bit ridiculous to keep it fun and none of the stats held over from level to level. I believe players are ultimately social, and sometimes all you need to do is give them something to banter about.
Local Co-Op in a PC World
One thing I worried a lot about was making a local co-op game for PC. Admittedly, when we started AVNT, the core target was console and couch play. When we realized we didn't have the money for online play I knew that, despite being a ten dollar game, we were going to get a lot of grief for asking PC gamers to crowd around their monitors. While this is true to an extent, the number of players that share my love of couch co-op surprised me. Each year it gets easier and easier to plug your computer into a TV, and connect some gamepads. Sitting next to your fellow player is something amazing, and sometimes you forget what that's like. While I understand for many it may not be an option, for those that it is, I think we need to support games that make this part of their design by voicing our approval. I know I appreciate all those that have done so for AVNT.
Worth the Pain?
While making co-op a first class citizen in A Virus Named TOM was difficult on a small team, I have to say there was nothing nearly as rewarding as watching a group of players taking on the challenge of those cooperative levels. To hear them ribbing one another's failures, bickering over a solution, laughing over griefing one another, and the elation after a hard fought victory, was nothing short of moving. It's as if each additional player multiplies my enjoyment of watching the process. There’s a strong temptation to create a purely single player game for a next title because of the sheer amount of work required by a small team to add legitimate cooperative play, but I honestly don't know if I can give up that feeling of standing behind a group of players and seeing the genuine interactions you've caused. Somewhat infectious you might say.
Ed. Note: If you're an independent game developer who develops cooperative games and are interested in sharing your Dev Story, please contact us at firstname.lastname@example.org.