Quick demo to show how weird it can get if you try to do arithmetic with too many digits. The pics show the scripts for the corresponding variables. See if any of them make sense to you... :) Made in response to AProductions' forum post about trying to do arithmetic with 20 digits, and the associated project (the original of this project) that demonstrates it.
From the differences in the scripts and results (compare 'a' and 'b') it appears that the Scratch(/Flash actionscript?) execution engine runs together some nearby operations (within the same 'refresh', I guess?), thus giving different results depending on whether or not that 'wait' is placed between the 'set to 111111111111111111' and the 'change by 1'.
