The main problem with these trick programs is that as a software engineer of n years I don't debug programs by staring at them for a long time or by memorising

The main problem with these trick programs is that as a software engineer of n years I don't debug programs by staring at them for a long time or by memorising a lot of tricks. I usually do it by running them and checking their output, or by catching runtime errors in a debugger. Writing software is not a one way process, it's a skill or an interactive process with the machine.