Oops! This week's puzzle comes a few days late. I got lost in P&A on Saturday, and forgot about my own puzzles. Shame on me. And next week is BAPHL 5 and the week after that is DASH 4, so I need to make a special effort to stay on time with my updates.
ETA (4/19): Double oops! I accidentally uploaded a second copy of Spiral #11 by mistake. I have fixed the error, and uploaded new files.