Planet D is, as the in-game description boasts, a "unique and challenging" game mode that differs from the Classic Challenge in two key areas. Firstly, each level has its own weird gimmick, such as being set at night or having balloons instead of boulders. Secondly, changing the difficulty level only seems to increase the length of the levels, and not their actual difficulty. In fact, on Hard or Insane you'll often find yourself finishing levels with more time to spare than on Easy or Medium.

Regardless of difficulty, there are only two levels in Planet D that should give you a hard time. That being said, though, it's still a fair bit harder than the Classic Challenge, and ideally you should max out your stats before even thinking about attempting it. Having 500 DNA saved up to get the strength boosts helps as well.

This first level shares some similarities with the Planet D speedrun, and gives you a sample of what to expect in the following levels. There are a fair number of stegosaurs and triceratops running around, and lizards are raining from the sky. Higher difficulty levels add a sprinkling of giant meteors just to keep things interesting. Being the first level, it's nice and short, and you can probably get through it without too much effort. Don't let it fool you into complacency, though. There's a lot worse in store.

Balloony Loons is, if anything, even easier than Arrival, and arguably the easiest level in Planet D. This is due to its gimmick: all the boulders are turned into balloons, meaning you can easily ram them aside without slowing down. Meteors will still be meteors, but this shouldn't be too much of a problem unless you have Meteor Storm turned on. On Hard or Insane you can finish this level a good 30-40 seconds ahead of the Doom Wall, so don't worry too much about failing here.

This is where things get interesting. While Planet D generally has more Dactyls than Classic Challenge, Hot Dactyl Mess turns things right up to 11. As well as swarms of burning Dactyls, the level contains immense flocks of Dactyls for you to hitch a ride on. The higher the difficulty, the denser the flocks, to the extent that on Insane difficulty they can fill the entire screen.

Needless to say, this provides an opportunity for some serious Dactyl Chaining. If you haven't gotten the Dactyl Chaining achievements yet, you can earn them here without even trying. If you do have the achievements, then shoot for the highest Dactyl chain possible: a x10 Dactyl Chain (which I have managed here before) will net you about 13,500 points. Factor in the constant bombardment of Dactyl Eggs, which are worth 500 apiece, and you can earn a LOT of points here.

Made it through those first three levels without using any Time Shifts? Good. You'll be needing them.

This is the first of the two difficult levels in the game. As you can see from the screenshot, it's set at night, and while you can still see where you're going, making out details can be very tricky. What's more, it's hard not to get psyched out by the ambience: there's no music here, just a low, ominous rumbling in the distance. Is the Doom Wall catching up to you, or is it just your imagination...?

To top it all off, the Doom Wall moves surprisingly quickly here. Even in a good run, you'll be lucky to pull out ten seconds on it. It's easy to make a mistake, slip up, and be devoured here, but with practice you can sail through it reasonably comfortably. If you're not fully prepared to tackle Planet D, however, this is where you will find out.

Once you've made it through After Midnight, the difficulty simmers back down again. Rollin' on D isn't as hard as its gimmick would suggest: while the level contains a ton of boulders and meteors to dodge, the time limit is pretty generous, so even if you get stuck on the boulders a few times, you should still make it.

If you have enough spare DNA for the strength boosts, this is where they'll really start to come in handy, as you can quickly boost your way through the worst of the boulders. If you're really lucky, you might also come across a strength power-up or two. Alternatively, just as Hot Dactyl Mess was a great place to practice Dactyl Chaining, Rollin' on D is a good place to practice boulder running. Just don't spend too much time practicing, or the Doom Wall might catch up to you.

Meltdown Derby is an interesting level because it can end up being either very easy or very tricky, depending on how things turn out. Similar to Hot Dactyl Mess, there are a lot of Dactyls here, both normal and flaming - there aren't quite as many, though, so racking up Dactyl Chains is harder. There are also massive herds of Parasaurolophus, and these guys can either trip you up something chronic - especially since you can't kill them - or they can provide a very helpful speed boost. Higher difficulties throw stegosaurs and triceratops into the mix to give you even more obstacles to avoid.

I'd recommend using the Dactyls to bypass the level's hills and mountains - this is a viable strategy anyway, but here especially it can save you some precious seconds. The Parasaurolophus can also help speed you up, if you can manage to get onto one, but you'll lose out on eggs and critters while you're riding them. They also have an annoying tendency to get stuck on bits of scenery, and on higher difficulty levels you can find big groups of them blocking the way, requiring a well-timed jump to get past.

Ready for the final level? You'd better be. Paradise Lost is almost as short as the first level, but it's also definitely the hardest. Why? Its gimmick is that the Doom Wall starts off RIGHT BEHIND YOU. You can easily outrun it, to be greeted with calming ambient sounds in contrast to the ominous rumbling of After Midnight, but a single mistake will send you right back into its clutches. You know those pillars you have to jump across, and if you fall you'll reach the area where the Spino egg is? You'll face that here without fail, and whatever you do, DO NOT FALL: it's tantamount to suicide.

I hope you have plenty of Time Shifts saved up, because you just might need them. As I said, though, it's a pretty short level, and once you've cleared it, that's Planet D over and done with.