What happened Roblox Corporation (NYSE: RBLX) shares plunged in Thursday trading to close the day down 7.8%. This was the second day in a row of prices falling since the company reported blockbuster sales growth in its first earnings report post-IPO. So what Two factors appear to be contributing to the declines. First: Competition. As videogameschronicle.com reported late Tuesday (perhaps not coincidentally, just hours after the earnings report that sent Roblox stock flying), video game producer Ubisoft is shifting its business model away from relying solely on sales of high-price "AAA releases" and evolving to offer a "high-quality line-up that is increasingly diverse," including "building high-end free-to-play games." Image source: Getty Images. Free-to-play gaming (plus in-game sales for a price) is, of course, Roblox's forte. Investors may see competition from Ubisoft in this arena as a reason to question Roblox's growth prospects. At the same time, a midday report out of investment bank Stifel Nicolaus yesterday, in which the analyst raised its price target on Roblox but warned of "decelerating" growth in April "that we'd anticipate continuing into the 2H as the biz laps difficult comps," may also be weighing on the stock. Now what Even if Roblox's growth rate is decelerating, it's got a long way to go before anyone could call it "slow." In Q1 2021, the company says it grew revenues 140% and bookings (i.e. sales of Robux) by 161% -- which actually might imply that sales growth is still accelerating at this point. Moreover, it's worth pointing out that on the company's cash flow statement, Roblox translated $387 million in sales into $142.2 million in positive free cash flow (FCF) in Q1. That works out to a free cash flow margin of 36.7% -- below the roughly 50% margin the company boasted heading into its IPO but superior to the 21.4% FCF margin Roblox booked a year ago in Q1 2020. With sales growth still strong and free cash flow margins arguably improving, Roblox investors might want to look at today's sell-off as a buying opportunity. 10 stocks we like better than Roblox CorporationWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Roblox Corporation wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of May 11, 2021 Rich Smith owns shares of Roblox Corporation. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source