King Digital Entertainment, the British developer of mobile phone puzzle game 'Candy Crush Saga', has filed for US initial public offering (IPO), in a bid to raise $500m for operational capital and acquisitions, which would value it over $5bn. King reported 7,000% rise in profits last year, with revenue and net profit reaching $1.88bn and $567.6m, compared to $164.4m and $7.8m respectively in 2012.