Confirmed; the platform tutorial is unplayable in Opera 10.10, Linux. This has been an issue for years, where web devs develop for all other browsers, which have extremely sparing keyboard controls. So web devs think they can just hook onto single keystrokes willy nilly. Well, these things never work fully in Opera, because Opera has assigned browser functions to single keys for years (since 4.x, I think, at least?).
FWIW, Opera has a preference to disable single key hotkeys, but that still didn't help in the platform game, because pressing comma in Opera activates the search-as-you-type.
Maybe you need a way to let people remap. But it would be worth mentioning at the outset that Opera users will run into these issues.
Everything is fine in FF. It was the Galaxy demo, but I tried the others too and they aren't working in Opera either. The Mario one does work, except the space bar Pages Down, so it isn't playable.
FWIW, Opera has a preference to disable single key hotkeys, but that still didn't help in the platform game, because pressing comma in Opera activates the search-as-you-type.
Maybe you need a way to let people remap. But it would be worth mentioning at the outset that Opera users will run into these issues.