we want some kind of exponential growth function that gives less weight
on lower progress boundaries but high (exact emulation) near progress
value of 1.
so here is how the current growth function looks like
progress    weight
0.1       0.0001
0.2       0.0016
0.3       0.0081
0.4       0.0256
0.5       0.0625
0.6       0.1296
0.7       0.2401
0.8       0.4096
0.9       0.6561
1.0       1.000