@OneLeggegRhino - Controls ae configurable from the main menu. That said, arrow keys won't work by themselves because diagonal movement is a necessity.
My personal preference is a WASD variant, with QEZC being the diagonals and S being wait. Left and right arrows swing my sword.
@aaasssddd123 - Blue doors open when all required rooms on a level are cleared. Episode 1 (this game) contains levels 1-4. Level 1 Sense North, Thrice West can be escaped - make sure you strike the orb!
I completed this game without having found the oxygen tank. It is possible to pass through the room two before the end (where sunlight shines into the water) without it. To do this, you need to use the sister as a sunlight shield for Robby. You can slowly advance up the jumps, taking care to press space to let Robby fall to the ground after each one so the sister can triple jump above him to cool him off. Once you hit the water portion, switch to Robby and sacrifice the sister.
Unfortunately, as I discovered, if you do this, that room becomes a one-way trap. Even if you choose to continue the game, you cannot pass through it heading east.
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 "Linx"){kind=icon}
Nice.