My latest invention is SSB Playground: play with the bitcoin bug commonly called the Sighash Single Bug. I demonstrate that it lets you do a basic form of transaction introspection and even enforce restrictions on the output count of future transactions.
Play with it here:
Or check out the source code: 
SSB Playground
GitHub
GitHub - supertestnet/ssb_playground: Create and test SSB restrictions -- bitcoin scripts that use the Sighash Single Bug to do introspection on a transaction's input count and output count and place restrictions on them
Create and test SSB restrictions -- bitcoin scripts that use the Sighash Single Bug to do introspection on a transaction's input count and outp...