The trailer featuers in-game graphics, as well as the in-game HUD and cockpit.
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For those of you who do not know, the old Mechwarrior reboot trailer marked the return of the Mechwarrior franchise. The company had some trouble getting backers, and had to shelf the game for a while. Last November, they had an unveiling for Mechwarrior Online. They could not find a publisher for the first iteration, so they decided to do it all themselves, leading to a free-to-play model (much like League of Legends) and a persistent online-only game world that evolves day by day (literally. Each real life day is a day in the game universe). This will allow them to release mechs, weapons, etc as the universe continues to move through its timeline.
I've been following this since before its official announcment back in November, and I'm very happy to see it starting to come to fruition. Expect gameplay videos soon, as Pirhana Games is at GDC and do have a demo planned. Beta should start soon after, as the game is planned to release this summer.