Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Stocks were a tale of two markets Friday, as the Dow and S&P 500 moved in different directions. The Dow rose due largely to some high-profile gains in two influential card network companies, but broader market measures fell almost half a percent. Still, the gloomy mood didn't hold back shares of Electronic Arts (NASDAQ:EA), Illumina (NASDAQ:ILMN), or BlackBerry (NYSE:BB), each of which posted solid gains today.

Electronic Arts rose 12%, defying a negative trend that affected most of the video game industry over the holidays. Although the NPD Group cited an overall decline in sales of console and handheld-game software during December, it also highlighted EA's latest entries in the Battlefield, Madden, and FIFA series among the top 10 sellers for the month. An analyst at Cowen argued that EA's total sales jumped 40%, allowing the stock to avoid the fate that game retailer GameStop (NYSE:GME) suffered earlier in the week. Moreover, analysts at CRT Capital recommended the stock, setting a $26 price target on the game maker's shares.

Illumina gained 9% after giving details about its strategic road map last night in a press release. The genetics company expects to expand its use of next-generation sequencing technology in areas like the reproductive health and oncology fields, as well as attacking emerging markets. Moreover, Illumina presented products to simplify preparation and analysis of genetic samples, along with its plans for increasing use of genomics in clinics. With some setting the size of Illumina's potential market at $20 billion, the stock could have further to run even after its big gains lately.

BlackBerry picked up 6% after getting a rare positive recommendation from renowned short-selling research group Citron Research. Citron believes that despite BlackBerry's failure to capitalize on its smartphone opportunities, it still has potential as an enterprise software company. With new CEO John Chen taking substantial steps in that direction, Citron put a $15 price target on the stock. Given the number of short-sellers who have bet against BlackBerry, any kind of squeeze could easily send shares soaring higher in the weeks and months to come, even without any fundamental company news.