Thanks for playing - yes, it’s quite a difficult game! To answer your questions:

• The player also has 8-way movement - controls are WASD QEZC. See the itch.io page for full keyboard controls; the next update will also add a settings menu where you can see and change the keybindings, but we’ll wait until the judging for the jam is complete before publishing any new features.
• Most of the time you can either step around the guard diagonally, or wait for them to wake up and wander off if they don’t see you. Attacking often leaves you in a bad position, and that’s intentional, but there are a few situations where guards totally block you in with no recourse, which we’d like to fix in future updates.
• Aira (the player character) crouches down to take cover if she is immediately behind an object or a wall, so a guard on the other side of the cover won’t see her even if the tile is in their vision cone. This is communicated to the player through her crouching sprite, but it would be good if we could indicate cover more clearly.

Invincible or invisible? Either way that’s definitely not supposed to happen. Please could you tell me what browser you’re using, including the version number?

I know there are some Firefox users who can’t play at all, but this seems to be a different issue which you’re the first person to report. The game works best on Google Chrome in our testing.