- In single player mode, you can repeat any level with all your acquired weapons and upgrades. It's best to do this in between levels because you'll lose your progress in the current level when you do it.
- You don't need to complete a level in order to save any upgrades, collectibles, weapons, completed challenges, etc. that you find. They're saved to your profile immediately upon acquisition. This is most relevant if you're replaying levels for things you missed.
- Starting in the second level, a secret will give you access to a weapon one level earlier than you would find it via regular progression.
- Consider waiting to use weapon mod bots if you haven't yet found the weapon in a level.
- Targeted detonation is the clear winner in rocket launcher mods and the mastery effectively doubles the power of the rocket. IMO this makes it the game's most versatile and effective weapon.