Antacid medal is wonky. It says "Kill 5 acid blobs" but I had to kill at least 20 or more before it awarded that. I didn't keep track of exact number but I know it was a hell of a lot more than 5. I just recommend anyone who is missing that medal to keep replaying the last stage and grinding acid blobs doesn't matter if you die a bunch or restart that level a bunch -- pretty sure it's keeping a global counter so it's fine and this should work (worked for me anyway)
Controls are, well, wonky, but the game has a better-than-average quality to it. 4 stars seems fair.