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

What: Shares of Glu Mobile (NASDAQ:GLUU) rose more than 23% Thursday after the freemium game specialist announced better-than-expected fourth-quarter results and a new game featuring singer and songwriter Katy Perry.

So what: Quarterly adjusted revenue rose 78% year over year to $76.2 million, led by the "ongoing traction" of its Kim Kardashian: Hollywood, Racing Rivals, and Deer Hunter 2014 titles. That resulted in a 57% increase in adjusted earnings per share to $0.11. Analysts, on average, were only expecting adjusted earnings of $0.02 per share on sales of $63.8 million.

In addition, Glu Mobile signed a five-year exclusive mobile gaming partnership with Katy Perry, under which it will create a free-to-play mobile game using her likeness and voice to be released in the second half of 2015.

Now what: For the current quarter, Glu Mobile expects adjusted revenue between $50 million and $52 million, which should translate to an adjusted loss between $3 million and $1 million, equating to a per-share loss of between $0.03 and $0.01. Curiously, analysts were modeling significantly better first-quarter earnings and sales of $0.03 per share and $58.2 million, respectively.

For the full year 2015, however, Glu Mobile sees adjusted revenue between $245 million and $275 million, and adjusted net income between $0.23 per share and $0.28 per share.The mid-point of both ranges sits above Wall Street's expectations for adjusted 2015 revenue of $229.3 million and earnings of $0.24 per share.

In the end, Glu Mobile did have a great fourth quarter and sealed an encouraging deal with Katy Perry. However, I'm personally still skeptical given the difficulty in consistently pumping out and monetizing free-to-play mobile games, the target audience for which tends to be fickle in their loyalties. For now, that's why I have no problem continuing to watch Glu Mobile from the sidelines.