The difference between a roller coaster and a ring tailed lemur is that when one has a problem it's a mild irritation and when the other has a problem it's a cause of unbridled panic and overwhelming guilt. There are stressful components to every management simulation game, but where Planet Coaster's mechanical breakdowns make me worry briefly about profits, Planet Zoo's biological breakdowns make me feel like a neglectful, abusive monster who should be dragged off to jail and never allowed near another living creature ever again.
Planet Zoo has several official modes—Career, Challenge, Sandbox, and Franchise—but its two actual modes are Things Seem Fine and Oh God What Have I Done. My elephants, giraffes, orangutans, panda bears, and dozens of other beautiful creatures can starve to death or die of dehydration if I'm not careful. They can contract diseases or get injured by fighting one another for alpha status. They can feel fear and stress and lack of privacy and the effects of isolation. They can overheat or get too cold. They can kill each other if you put the wrong animals together in the same habitat. At one point I saw protesters carrying picket signs in my park. It was because my giant burrowing cockroach's glass box was slightly too humid for its liking. I couldn't even keep an ugly bug that eats dead leaves happy, and I instantly felt terrible about it.
Planet Zoo isn't just a management sim, it's a survival game. In fact, forget that I just compared it to Planet Coaster. At its most stressful, Planet Zoo is more like Frostpunk or Prison Architect. None of the lives you're in charge of actually want to be there, and making a mistake puts those lives in danger. This is mostly a good thing—stressful experiences can be a weird sort of fun, and heart-wrenching guilt should be a feature in more games. But some of the stress of Planet Zoo is due to parts of the game not working that well.
Gibbon Architect
Take my current zoo, which I've named Zoo Bisou. It's still small with only a few habitats—two bears, two wolves, two nile monitors (giant lizards), one Galapagos tortoise, plus enclosed glass exhibits featuring two tarantulas and two snakes. I've been getting notifications for a while now that my bear's habitat is a disease risk because it's not clean, but repeatedly sending one of my zookeepers over to vacuum up enormous bear turds hasn't made the notification go away. After several frustrating minutes I finally make a guess that the issue might be the small river running through the back of the bear's habitat—even though the water looks fine ('Water View' mode doesn't show any alarming red danger zones). I install a water purifier and the disease risk notification vanishes, but Planet Zoo didn't make it clear that the water was the problem, and it should have.
And in the time it took to figure that out, I now have nine giant lizards instead of two, because one gave birth to a huge litter—so I have an overcrowding problem in that habitat. I also now have roughly 20 tarantulas (not only did my original pair give birth but their offspring have matured and reproduced incestuously), three more snakes, a new wolf cub, a new bear cub, and some protestors picketing because my turtle is sad that it doesn't have any toys. Plus, one of my zookeepers is complaining that he can't find his way to the staff room, which I discover is because he's somehow fallen through the map and is wandering around underground. Taking the time to solve one problem gave literally everything else in the zoo time to develop their own problems.
This combination of legit problems and game flaws isn't a complete disaster. The spiders giving birth means I can sell a bunch of them for cash, useful since I'm not currently operating at a profit. I can make my lizards' habitat a bit larger and start feeding them birth control pills so they don't produce another unexpected litter. I release my surplus snakes into the wild, which earns me conservation credits that can be spent on rarer animals, and I put a vet to work researching the tortoise to find out what kind of toys it likes—something I wish I had to option to do before I adopted the tortoise. (Unfortunately, research can only be undertaken when you've actually got the animal in the park already, which feels pretty irresponsible.) My underground zookeeper, meanwhile, has quit in frustration, so I drag him to the zoo's exit (he can't find it himself, naturally) and hire another.
Animal kingdom
With the exception of Sandbox mode where you have a bottomless wallet and the ability to turn off things like animal sickness, injury, and death, Planet Zoo is an extremely busy an occasionally exhausting sim. exhausting. Everything needs constant attention all the time—not only keeping your animals healthy but your staff happy, managing your budget and zoo's reputation, and dealing with day-to-day concerns like preventing guests from vandalizing park benches (by hiring a security guard and installing cameras) and making sure habitat walls don't get so dilapidated they crumble and allow a tiger to terrorize the park (the guests won't get mauled, but they do leave the zoo in a hurry). This is also the reason the sign I'm building at the entrance of Zoo Bisou currently only consists of a Z. I just haven't had time to finish it. There are always incestuous spiders and unhappy tortoises to sort out.
Seeing babies appear, even if they're spider babies even if they're far more spider babies than you were expecting feels good
At times all this stress and guilt and micromanagement makes me feel like I should just play in Sandbox mode, and I've tried. But honestly, it's just a bit dull in there without all the worries. In Planet Coaster, there's a real enjoyment to be had from building a nice park and just sitting back to watch the guests ride the rides, but Planet Zoo doesn't give me the same feeling. I enjoy watching my animals, but I don't enjoy watching my guests watching my animals. Seeing visitors screaming on a Hammer Swing or a Hellion Ring or custom roller coaster is way more fun than watching them briefly stop walking to stare through a glass wall at a bored bear or a sleeping red panda. Lovely as Planet Zoos animals are, they just don't pack the excting punch of a custom coaster.
But the animals are really beautiful. Their sounds and animations are wonderfully done—apart from a few glitches when they're trying to climb things or move between different environmental features, at which point a leg might stick out at an awkward angle or they might stutter-step around. They seem real enough that it feels genuinely good when you see you've made them as happy as imprisoned animals can be. And seeing babies appear, even if they're spider babies—even if they're far more spider babies than you were expecting—feels good too, because it means you've made your creatures comfortable enough that they're willing to make more of themselves.
Zoo d'état
The number of options you can fiddle with in Planet Zoo is impressive. You can place prebuilt structures, but you can also build them yourself out of individual parts in the same comprehensive but occasionally finicky fashion as in Planet Coaster. Personally I don't have the patience for building elaborate custom exhibits, but seeing what creative players have done with Planet Coaster makes me excited to see what they'll create with Planet Zoo's extensive tools. Management options are pretty deep, too, and you can assign your workers to specific shops or zones or individual habitats, which is a must when certain areas get continually messy or dilapidated. You can even dictate exactly what each employee's responsibilities are (one person's entire job could be just vacuuming up enormous bear turds, if you wanted).
The layers of micromanagement extend all the way down to elements like which colors of balloons you sell in a particular vendor stall and how much to charge for each individual color, and Planet Zoo will even show you the profit margin for each. I don't typically need or want to dive that deeply into the menus, but I have found it useful when I needed to wring out some extra profits during a budget crisis. (Also, you can pop the guest's balloons by clicking them on them, but I haven't seen anyone go back to buy a replacement.)
Hopefully post-launch patches will arrive to fix some of the issues I've had with unclear notifications, subterranean zookeepers, and a few other glitches. I'm happy to endure the stress and guilt over the lovely creatures of Planet Zoo, but I definitely don't need more of it than I've already got.