I've been playing Factorio for a year now and I've always been disappointed with our relationship with the biters. Their balance and behavior seems like a less than ideal choice for this game. For example they are always bee-lining for the turrets instead of avoiding the source of pain and death. Although they are motivated by pollution, they try very hard not to get to the pollution sources. They are sooo fast for such large creatures, and die by the dozens in seconds to a single turret before they can touch it. The spitters seem to have overpowered shots considering their range. It all adds up to a wierd dynamic of zombie-like behavior and crowd control.
I would much rather see them smarter, slower, tougher, and "mazable". I use the term "mazing" as a reference to tower defense games that allow you to generate mazes that the creeps have to get through in order to reach your base. So far the current aliens are generally content just chewing through walls while being shot rather than pathfinding through them. So mazing doesn't work at all.
I'd like to recommend the following changes to biters which I think would add more depth to our interaction with them.
- Biter stat changes: Ramp up the HP some and slow them down accordingly. There should always be a weak biter that can outrun the player. Perhaps this would be a separate creature that is produced abundantly but always sticks with a biter parent prior to coming close.
- Change biter behaviors so they are more likely to avoid turrets if they see them and can't reach them. I'd say the lower tier biters should avoid them altogether.
- Change biter behaviors around walls. They should attack walls only as a last resort if they can't find a way around. They're animals, they are motivated to destroy the pollution source not eat concrete.
I also have a pathfinding idea below, slightly off topic.
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Coding wise- You don't want to let the AI cheat and have some powerful pathfinding that lets them see the one entrance at the back of the base from half the map away. They would make decisions based on a "decision radius" but would also probably need some sort of memory. There's a neat tower defense game called "Ant Buster" http://www.rstein.org/antbuster/ that uses a pheremone system to guide the ant pathing. I saw a biters pheremone thread here on the forum too. The basic idea is to let the biters try to get in and not get hurt too much but make local decisions. Past actions influence the next wave of biter choices.
If pheremones were incorporated then that would greatly influence the decision making. They way it works is each biter lays down "bread crumbs" that previous biters follow. There is some randomness but the priorities go pollution first, pheromones second, random veering third. The bread crumbs add up, which can make for a strong pheromone trail that overrides the pollution factor. This means that trailblazers are mostly motivated by pollution, but followers are more motivated by the trail. But then there's "splat" pheromones and "come over here" pheromones. If a biter dies, there's a zone around him that warns away other biters so they will choose directions skirting the splat zone but still considering their other priorities. And if a biter attacks something, then it emits a rallying pheremone to attract the other biters.
In factorio the biters don't bring food back to their nest, so an important component of scouting and long-range rallying would be missing with this system. But if biters were allowed to double-back, then they would be laying strong trails to encourage biters at the nest to follow their route to an important place. That's how ant scouts work.
All of this lends itself to coding fairly straightforwardly. It is done with nodes across the landscape, created by the biters, with a positive (follow this) value or a negative (don't go here) value. Biters have default priorities (follow the pollution gradient) but are also influenced by the value of the pheremone nodes. As a node closer to the pollution has a higher priority than one closer to the nest, the biters go to towards the pollution. Wala! Biters with a non-cheating pathfinding AI that makes them smarter than they are now but should be relatively CPU friendly.