Glad to hear you're enjoying it! Alas, the tutorial does end after you press play; the greyed-out levels are works-in-progress that aren't in-game yet. I could definitely do a better job making that clear.
I'm currently trying to get more funding to keep working on the game and add more levels. Following the game here or joining the mailing list will letcha know when I update it.
I'd love to hear any other feedback you have about the game, so don't hesitate to give me a shout. :)