Over the last few days I've been thinking about how zombie difficulty should work in the upcoming Outbreak game mode. Outbreak will feature a dynamic difficulty system that will make the zombies easier or harder depending on how well you're playing. This will result in a fun challenge regardless of your skill level or how difficult the map is. There are a few factors to consider when doing this though. Firstly it needs to be fair and not penalize good players. Secondly it needs to accurately determine the ideal level of difficulty (the perfect fun challenge) and aim towards that. Finally it needs to adjust the zombie difficulty in a fun and intuitive way. Anyway after much pondering and testing here's how it's going to work:
1) Each team will have its own dynamic difficulty value. This means that if one team is full of pros and the other team is full of newbs BOTH teams can have fun. The pros will be facing hard zombies and the newbs will be facing easy zombies, making for a fun time for all. Don't worry though, there is an incentive to play well as you will be rewarded for facing harder zombies.
2) The dynamic difficulty value will change the TYPE of zombies that you face! Originally I had it multiply with the zombie's hitpoints, but this new system is better. Basically there will be 3 main types of zombie that will spawn at different frequencies depending on your team's dynamic difficulty value. The easiest zombie will be slow but with lots of hitpoints, the hardest zombie will be fast with few hitpoints, and the medium zombie will be in between. As you play better and better you'll start seeing more fast zombies spawn and fewer slow zombies. This has an inbuilt penalty and reward, making the zombies more challenging but rewarding you as your team can finish the round faster.
The slow zombies are very easy to survive against as you can always kill them before they reach you. The problem is that they have extra hitpoints and take longer to kill. This is important because I've reworked the objective of the game to be the first team to kill X zombies (let's say 1000). As the speed of zombie killing is directly related to how much health they have, you don't want to be facing the slow zombies for too long because it takes longer to kill them and the enemy team will beat you.
The fast zombies are very difficult to survive against because they'll just swarm all over you and kill you. However if you and your team are good enough you'll be able to withstand a higher ratio of fast to slow zombies. Surviving against these fast zombies will be a challenge, but if you can pull it off you'll be rewarded because they die much faster. This allows your team to reach the 1000 zombie kills target before the enemy.
The majority of players will be facing medium zombies, with extra fast or slow zombies thrown into the mix as their dynamic difficulty value goes up and down. There's an incentive to play better if you can, because then you get to fight against the faster/weaker zombies and gain kills at a faster rate than the opposing team. And of course if your team is struggling you'll naturally end up fighting against the slow zombies which will give you some breathing room and still make the game nice and fun. The end result is that both teams have fun and strive to do the best they can.
3) The final consideration is HOW to determine if the game is too hard or too easy? What makes for a perfect fun challenge? It used to be the bomb activation rate but we can't do this any more because bomb's no longer have activation rates. The 'activation rate' is now determined by how quickly you kill zombies. So what else? Well, this still needs some consideration but at the moment I'm leaning towards your average health. A fun game is one where you're permanently on the brink of survival. You won't want to die too often, but you don't want to just sit there holding down the trigger either. Ideally you want the zombies to be just fast enough that they're able to hit you but not completely overrun you (unless you make a silly mistake of course). This is the sweet spot that encourages you to fight back harder, move evasively, set up traps with cars, use your skills, and coordinate with your team to gain every little bit of breathing room as you can. By playing better you can keep the zombies at bay until they get too fast for you to handle. At this point they'll start damaging you and your teammates and threatening death. However here's where the dynamic difficulty kicks in, sees that you're starting to take damage and makes the zombies easier again. This keeps you perfectly challenged while at the same time rewarding you for playing better because the zombies are now dying faster and you can earn more kills per minute.