10x10:d2aBeBBcBcBf3a2gBjB3j2gBaBf0c1cB0e2a1d
12x12:BaB0c2a1bBBc0BbBaBaB20bBkBa1j1b1BbBB2b1a2aBj10b001B0eBk0bBb2gBb2bBa2aBi1a
45x31:Bn1f1fBnBc2zk1i1bBcBdBg0dBc0b1zzb1d1za1dBw3c1v0n1i1n1k1a2uBa2o0nBa0n1i1n1gBnBi0d1aBq2aBd1hBm0k1m0e0o1e1o1l1b1hBa1hBbBi1nBdBcB
Pretty difficult, but reasonable
10x15:b0BbB0eBb2d1b1Bb2n2b2m1cB0c1aB0d0Ba1cB0c1mBb1nBb2Bb0dBb2e1Bb0Bb