Wow, that's annoying. That's L4, right? There should be keys just below the shop, one all the way at the other end of the corridor from that goal, and one at the rightmost room in each of the two horizontal corridors with two teleporter pads -- the middle two of the four horizontal corridors.

If you're still reading, can you tell which one is missing?

Thanks for reporting this! We've fixed it and uploaded a new version. Make sure you shift-refresh the page to get a new version.

Yeah the new version is better