[eru]

Wouldn't this need to know what I actually did instead?

When I use it, it tells me that the form was incomplete. I tried to figure out how much I regret having bought 0 bitcoin so far.

Perhaps needs a better error message? I think it actually doesn't like the zero, but prevents it doesn't like incomplete data. Zero is also a number.

> CAUSALITY_ERROR: You cannot SELL before you BUY.

https://en.wikipedia.org/wiki/Short_(finance)

Needs at least a better error message that short sells aren't supported, instead of trying to be too clever by half about causality.

[b0bbi]

Thanks for the "zero", it really does matter in a calculator like this.

Fair point on the shorting - I definitely prioritized retro drama over actual market mechanics there!

[eru]

Well, 'zero' is what I actually did. For regret, you'd need to select a counterfactual of what I could have done. (And at least one of them needs to differ from zero to give you any results. Or more generally, two scenarios need to differ in at lest one aspect to produce a meaningful comparison. Identical scenarios in back-testing give identical outcomes here.)

[b0bbi]

fixed, btw

[eru]

Thanks!