"The small green bug crawls through the window into the room."

Translation: A kicsi zöld bogár bemászik az ablakon a szobába.

[Sir-Nicolas]

can somebody explain me why is it "bemászik"? i wrote átmászik as i learnt it...

[vvsey]

"Be", here, is referring the room. Into the room. "Through" (the window) is understood.

I can refer you to the reverse exercise where this sentence is discussed in detail:
https://www.duolingo.com/comment/17746472

[fiderallala]

I was allowed "kicsi" but not "kis". Is there a significant difference between the two or is this an oversight?

[jzsuzsi]

Both kicsi and kis are good here. (And now both of them are accepted)