[Exploit?] Rainbow spiral design

[Draco18s]

The listed benefit of Rainbow is +100% spiral equation speed.

What it actually does though is reduce the maximum threshold by 53%

What this means in practice is that if an equation is 50% done to the next level, you can swap to the Rainbow spiral for a brief moment before switching back, and gain the full benefit of having Rainbow active the entire time while instead maintaining near 100% uptime on a different design (eg. Pi or Laser, which are per-second based).

You can do the same thing with Diamond and Lame, though there isn't really a comparable fix, as they're computed only during single frames when battle attacks happen, but are mutually exclusive with Orange & Purple Winding which may be the more powerful spiral design (and fixing the exp or math skill as incremental by percentage of the battle would actually make the problem worse, as it would allow O&P to be active the single frame of attack completion gaining full benefits of both designs, instead of only one).

<Programmer talk>

Spiral equations have a exp threshold that increases with each level, but for simplicity, lets say that it is 1000.
Spiral equations generate 1 exp/second. This means it will take 1000 seconds to level up.

Rainbow should make equations generate 2.1 exp/second but actually cause the threshold to be reduced to 476. This means that if an equation has 500 accumulated exp with 500 seconds remaining, switching to Rainbow instantly levels the equation instead of reducing the remaining time by (about) half to 238 seconds.