Got it, now I'm on 11.
8: Gur qvssrerapr sebz gur cerivbhf yriry vf vzcbegnag.
9: Guvf bar vf gevpxl, V unq gb guvax nobhg jul gur fbyhgvba jbexrq nsgre V nyernql tbg vg.
10: Abg gbb qvssvphyg, svaq fbzrguvat vapbzcngvoyr jvgu gur purpx.
If you're stuck at level 7, the solution you've missed is probably double-checking the king.
Level 8 is about White to Move, ergo Black just moved — but there's only one black piece that could have just moved, make that case impossible.
Level 9, there's a certain place black's knight can't be while black is also in check.