This is an implementation of @rdml's error correction. Inside are two custom blocks. The first one (the "encode <number> with block size <number>" block) encodes the number to make it error-resistant. The second one (the "error detect <number>" block) does the error detection and decoding.
There may be problems with large block sizes, due to how Scratch deals with very large numbers. A block size below 16 will probably work (above 15 there start to be minor errors in the decoding, but by 20 there are lots of errors). However, a longer block size means a smaller code, since there are fewer beginning codes.
