  We present the results and conclusions from the citizen science competition
`Observing Dark Worlds', where we asked participants to calculate the positions
of dark matter halos from 120 catalogues of simulated weak lensing galaxy data,
using computational methods. In partnership with Kaggle
(http://www.kaggle.com), 357 users participated in the competition which saw
2278 downloads of the data and 3358 submissions. We found that the best
algorithms improved on the benchmark code, LENSTOOL by > 30% and could measure
the positions of > 3x10^14MSun halos to less than 5'' and < 10^14MSun to within
1'. In this paper, we present a brief overview of the winning algorithms with
links to available code. We also discuss the implications of the experiment for
future citizen science competitions.
