Ah, Spring Yard Zone. That was a weird one, wasn't it? In retrospect, it's sort of a prototype for the Sonic games' "casino" type level, which got solidified in Sonic 2 with Casino Night Zone. And by "solidified," I mean "Sonic Generations and Sonic 4 Episode II copied Casino Night Zone wholesale without the least bit of shame." Thankfully, I'm not doing that, in part because there would be absolutely no way to implement half those pinball/slot machine things in the Jazz 1 engine, and without those you're left with what, Sparkling Zone? Hmm. Maybe it's not too late to consider a quick palette change...
Anyway, Gravis is a very animated planet! This is where I start getting really into graphical complexity, with both the walls and the skies given immense detail in areas you can't even see in that tiny resolution. You can also see in this screenshot a hint at the name's origin: Gravis was a company that made a PC GamePad that Epic promoted heavily within Jazz Jackrabbit 1. And since "Spring Yard Zone" is a really hard name to make sound like a planet, you get to tour the planetary origin of that gamepad instead! Gravis borrows a lot of its graphics from Industrius, which has been one of my favorite JJ1 planets for pretty much twenty years now, in part because it's got several different gimmicks--rockets flying you across spike pits, little platforms sliding in and out of walls, sucker tubes, even some thoughtful enemy placement. Of course, half the Sonic With A Gun planets outstrip Industrius in gimmicks by a mile, but still...
Besides animation, Gravis is also heavily focused around motion. Here you can see a bunch of Jump Around powerups, which increase your jump height, and to the right of the screen there's a diagonal spring. Expect a lot of those launching you around the level, either helping you over pits of spikes or just pointing you to goodies in the air. There are plenty of normal springs in Gravis as well, and bumpers, and moving platforms, and spike balls... well, that last one's not quite on message, but it's true there are a lot of them.
Of all the planets in Sonic With A Gun, Gravis might be the closest in style to the normal Jazz 1 levels, for a couple of reasons. One is that there are a lot of enemies--four different types, in fact, though maybe not the exact four you're expecting if you're familiar with Spring Yard Zone. (One got replaced, and another suffered a very necessary redesign.) Another is that Spring Yard Zone got a lot of mileage out of its curves, and Jazz can't run up walls, so some reimagining was needed. In the end, a lot of Gravis is broken into two parallel paths, one indoors with a lot of slow combat and spike dodging and one high in the sky with more platforming. Of course there are plenty of opportunities to switch back and forth between the paths, even when they're not outright merging.
Were these sequences, with their columns of 2x2 blocks in alternating syncs, any fun in Spring Yard Zone? No. But they're probably the single most memorable thing about it, so they had to be incorporated somehow. Look for them in the second act; every act of every planet has at least one feature that appears only there, not in the other act, just to keep things fresh. The reason for all those spikes is a sad truth: in Jazz 1, objects can only be solid from the top, not from the sides or bottom. Additionally, there's no mechanism for getting crushed to death. Every planet in Sonic With A Gun is a combination of my own ideas, references to Jazz 1, and references to Sonic 1, and in the third case, not everything can be ported over perfectly. But hey, if you wanted 1:1 accuracy of engine and level design you'd be playing Taxman's mobile remakes instead of this.
