LOVE this game. For those wondering about meters, here's what I've learned:
- Boost meter is the top semi circle over your ship. It constantly charges up, and while it charges it is lit up while the meter is filling. When it is full it stops glowing/goes a bit dark. You can only boost when it is full, but you can use a lot or a little, meaning you can boost more frequently using shorter bursts.
- If you hit enemies while boosting, you get a bit more boost, prolonging the duration.
-The overdrive meter is the bottom semi circle. It charges by gathering the green bits that float around from enemy explosions. Again, overdrive can only be used when the meter is full, but it goes through the whole thing once you engage it.
(Also: Use boost and throw human (L2) to really fling the little dudes around - they can go around the edge of the cylinder practically using this.)