A simple Binary Counting Program. Only 1 byte available, 0 to 255. Great for showing students the binary number system and fairly hard to break.
Running under WINE in KDE (Linux):
I wrote this program in middle school, mostly out of knee-jerk spite. I was newer to programming at the time, but the program we were using as the "intro to binary" in the programming class was, in my opinion, utter garbage: it included a text box for entering a number and some digits to toggle, but didn't validate the text box, and so it crashed easily and frequently. Not to mention, it didn't have any way to increment or decrement the number, which I thought would be useful for quickly getting a feel for the system.
That night, I went home and put this together. The class generally ended up appreciating it, though most were more confused why I bothered, and I learned a valuable lesson about SmartScreen and was able to witness people outside my family using my software for the first time.