Paz mentioned us hitting alpha a few pages back, but I figured I could mention a few specifics!
I'm a big fan of skyboxes and the goal is to have one per 'world' so I made the one for world 5 - you can see it in this gif (everything above the the short white wall with the vents in it is skybox)
and that's the new subboss that went in for Alpha, called Liquorice, and she's an enemy Android that operates under the same rules as the player. I wanted to do this fight from the start because I thought it'd be super cool and a good way to twist things around, but I was really worried about if it'd work or if it could feel right (we did a VS test early on in development and it sucked)
It was actually replaying Muramasa on the Vita that convinced me to go for it (those that have finished all the endings hopefully know what I'm talking about?) the symmetrical-ness of it was really cool and I loved that the reason WHY the enemy felt dangerous was because you knew just what they were capable of. So just like a player character, Liquorice has a battery, she can get knocked down but gets back up, her health will recharge if she doesn't get hit, she can steal the battery (so it's tug of war over who dies first) and she can use the players powerups. Her AI was pretty straight forwards but she does a bit of leading (which makes her a surprisingly dangerous enemy) and has a badass secondary weapon (which like the players weapon is on a cooldown)
her secondary weapon is a knife and when she uses it, she picks a target and high-speed dashes behind them and starts charging up this big omni slash. (in the gif, she then collects enough player orbs to level up her gun and because the player is downed, she's heading up to steal a powerup)
I designed the knife as if it was a player weapon so it'd feel believable, yet still have a tell so human players had a chance to get out of the way. All through the dev it felt like a huge gamble - what if it didn't work I'd have to strip it out and do something else, but it all came together, I was happy with it, we put it live and people seem to dig it, so, hurrah!