Tip to the developers: Check upgrade requirements on click, not just to enable the button. Clicking fast while it lags results in double purchases (or more).
This can be replicated by tools that allow really fast clicking. Setting my mouse driver to 1000 clicks per second, a low level unit with a + 100% upgrade easily reaches 10^(150ish) z. Yes, the number is shortened to z (whatever that is) but is still around 150 digits in front of it.
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