Riseup Game which was released 6 months ago has got more than 100 million downloads and they have not partnered with any publisher the indie developer himself have published from his account. https://play.google.com/store/apps/details?id=com.riseup.game&hl=en I did quite a bit of research but was not able to get any insights on how they were this successful.It could be really great if someone can give a bit of insights on how they did the marketing part
