In terms of the speedrun - I see the route is built around collecting them, but what is their exact function?

Thanks for any answers. :)

Radio: All three characters can use this. You use it to switch to another character on the fly, at any time, except during a conversation. You can't switch to a captured partner, obviously.

Ruby Ring: You'll need this to bribe some characters into helping you.

Lupin-exclusive items:

Vest: You'll be protected for one hit for each one you pick up.

Shotgun: Use this and you'll get a few three-way gunshots. But, you get knocked back a bit when you fire the weapon, so be careful.

Goggles: They help you find traps in some stages.

Bombs: They destroy all enemies on screen and open doors and passageways. Hint - use them on the fireplaces in stage one...

Jetpacks: Use them to fly around the stage. Get hit and you'll fall down.

Oxygen tanks: You need these to swim around. Some stages -require you- to go down and swim.

Balloons: If you fall down a hole, you'll be saved by this. You can shoot your gun and maneuver a bit while floating, but the balloon will pop after a few seconds of flight.

Tell me if you need any clarification or have any other questions.

Ah wow, thanks for the answer, and there's quite a lot of diversity there.

I messed around and starting making save states for this because I'm very tempted by how it plays. For Goggles, "traps", is that like in act 2 on the first stage? I noticed running through the first stage, sometimes rocks fell on me in the 2nd stage, but sometimes it didn't. What constitutes as a "trap"?

This is a very unique/underrated game. Thanks for answering.

The traps are just the things that make stuff fall from the top of the screen (rocks or bottles). They are invisible unless you use the goggles. They have fixed locations on certain screens (at least one screen in every stage has traps), but they behave like enemies in terms of spawning. If a trap isn't there it's because it didn't spawn, either because the route you took caused there to already be too many enemies on screen or you entered/exited a room which despawns everything. I tried mapping all the trap locations once, but gave up after realizing they were very inconsistent in terms of which ones actually spawned. The traps are the circles on the wall in this screenshot.