The The Ireland-registered makers of Candy Crush Saga have seen nearly US$1 billion wiped from the company's value after shares started trading on the New York Stock Exchange (NYSE).
The stock price for King Digital Entertainment plc dropped more than 12% within minutes, dropping its value by US$850 million (€615.7) to around US$6.25 billion (€4.52).
The initial public offering (IPO) valued the shares at US$22.50 (€16.29), with a total capitalisation for the firm of US$7.1 billion (€5.14).
But shortly after opening the price dropped to below US$19.50 (€14.12). It later eased slightly.
The flotation aim was to raise US$500 million (€362m) to help fund future development and expansion.
King has become hugely profitable based on the success of three games - Candy Crush Saga, Pet Rescue Saga and Farm Heroes Saga - even though it has 180 titles in total.
Riccardo Zacconi, CEO & founder of King Digital, rings the opening bell at the NYSE
The company has more than 324 million monthly unique users, and operates a website with 14 languages. However many investors have been wary of games firms with a limited range of products.
They cite the demise of one-time market leader on Facebook, Zynga, and its Farmville as an example to avoid.
King has its registered headquarters in Dublin and also has offices in Stockholm and London - as well as games studios in several European cities.
It was founded in London originally as Midasplayer Ltd in 2003 before King Digital was registered in Dublin last July, to assist in inter-country transfer pricing, and "intended to provide us worldwide tax efficiencies".
Midasplayer directors include Swedes Sebastian Knutsson (45) and Lars Markgren (50) and Italian CEO Riccardo Zacconi (46). Its website, through which players can buy 'freemium' game tokens, is domiciled in Malta.
In January, it posted a blog explaining its reasons to buy the EU trademark for the word "candy" and application for the US equivalent. It said the reason was to protect its intellectual property (IP) and thwart competitors trading on its name.
In its February US IPO listing document, King warned potential investors that unauthorised distribution or piracy, particularly in Asia, may harm its revenue and entail costly litigation to protect its IP.
