- Estimated achievement difficulty: 8/10
- Offline: 30 
- Online: 0
- Approximate amount of time to 1000: 40-60 Hours [depending on skill]
- Minimum number of playthroughs needed: 1 [mission select]
- Missable achievements: None
- Does difficulty affect achievements: No
- Unobtainable/glitched achievements: None
- Extra equipment needed: Couch co-op partner.
Welcome to Geometry Wars 3: Dimensions! For veterans of Geometry Wars, this entry to the series adds 3D levels and a new adventure mode which can be a little confusing at first. However, the game is still simple in theory; there are only four controls (move, shoot, bomb, super) using the joysticks and triggers. As is the case with past Geometry Wars games, practice makes perfect. Don't get discouraged if you can't beat something right off the bat. This game will definitely test your patience, so be ready to take a break and play something else if it drives you mad (like it did myself and my wife).
Huge thanks to Maka for the video guides and their descriptions.
Start off with adventure mode, making sure to level up each drone and super as you progress. Try to get three stars on every level for the "Geometry Warrior" achievement. But have patience. Take the time to upgrade your drones and supers, and replay missions once you have better gear. For adventure mode, certain drones help more than others. I found snipe, ram, and collect to be the best. However, if you are struggling with a level, keep trying drone/super combinations until you find something that works for you. There's a delicate balance between collecting geoms (which drop from dead enemies and increase your multiplier) and staying alive -- try to find it by using what works best for you.
After adventure mode, fire up classic mode, which should be extremely familiar to anyone who played Geometry Wars 2. Practice and patience will be the only things to help get you through them. There is a definitely a certain amount of skill required, but I've seen my friends succeed with practice and luck.
Oh boy -- the co-op section of this game. As tough as it is, I need you all to know that I got my wife, who had up to that point never played a video game, to pick up Geometry Wars 3, coached her a bit, and after a ton of patience and time, we were able to get all 30 stars. So, with that in mind, anybody with a bit of coordination can help you on these. Some levels can be won with just one player (I had to do that a few times), but the three stars will probably take both players contributing to the multiplier to obtain.
After beating adventure mode and upgrading the collect drone to max, go back and finish any level-specific achievements you have left.
I know it sounds like a cop out, but the only real guide for this game is practice and patience. It's not as bad as Trials Fusion in the skill-required department, but it's no cakewalk either. Just keep trying different combos in adventure mode and check out Maka's videos for level-specific help.
[XBA would like to thank Mercury for this Roadmap]