Ranked in these QuestionsQuestion Ranking
Pros
Pro Airboards
This recurring gimmick is fun enough to where I feel it deserves a very special mention. In some levels, there is an airboard somewhere or another which you need to use to progress. Once obtained, you can use it to basically fly for the next segment of the level (or, in some releases, the entire rest of the level due to a bug). So basically the game turns into a neat, loosely shoot 'em up-esque kind of game for a bit. Really fun idea!
Pro Large amount of content
Each episode has 6 levels each, split across 3 planets, and there's 9 episodes in the CD release, and 6 episodes in the original. Each planet tends to have some thing or another to make it stand out from every other planet in the game. Not to mention all the easter eggs and hidden levels, the branching stage paths that encourage a bit of exploration, etc.
Pro Nice, colorful graphics
The spritework certainly isn't perfect here, but the bright, colorful graphics, the decently smooth animations, the really fancy demoscene-esque visual effects, etc., all adds up to a game that can be very pleasing to look at in motion, even if perhaps not in screenshots.
Pro Good variety of weapons that are all helpful to some extent or another
The default gun works well enough as a fallback, the toaster is the default gun but easier to hit with and with an ammo limit, RF missiles are good for hitting multiple enemies at once and a bit above and below you, and Launchers are good for hitting large clusters of enemies closer to the ground or significantly below you. Also TNT can hit every enemy on-screen if need be.
Pro Great stage variety
The stages mostly play quite differently from each other, and the game is still introducing new ideas up until the literal final level. Tubelectric has Sonic-like tubes mixed with turrets that you have to time your way past to avoid getting shot at, Orbitus has walls that basically let you wall jump, Lagunicus combines dark levels and water levels in a way that somehow actually WORKS and is actually fun despite combining two widely-hated level types, Pezrock has swinging spikes balls that you have to avoid, Crysilis has fast-moving flying springs that you have to precisely platform across... the list goes on and on.
Pro Amazing soundtrack
Not every song in the soundtrack is perfect, but there's a large variety to the soundtrack. Favorites of mine include (but are far from limited to) Tubelectric, Medivo, Crysilis, Orbitus, and Lagunicus.
Cons
Con Episode B in CD release kind of sucks
Episode B in the CD release suffers more from screen crunch than basically any other episode in the game, especially when played on a high enough difficulty setting to where the zombie hands show up in Stonar, the second planet of the episode. But also Raneforus has monkeys that fall from the sky and there's basically nothing you can do to avoid that other than memorizing where they are. Not the end of the world, but in my eyes a notable low point of the game.
Con Screen crunch
Screen is way to zoomed in. The sequel fixed that, but it's not a DOS game. You may have to stop and start your way forwards instead of running full speed ahead a lot of the time sadly, in order to maintain a lower level of speed that actually works with the game's screen space.
Con Turbo mode is frustrating and not very fun
Turbo mode has enemies that move way too fast and hit you without much warning. You can learn the stages, but it isn't very fun outside a select few levels sadly.