Me, too. My brother and I played whenever we couldn't be outside, or needed a break from Legos.
One of the best aspects of the game is that it featured cooperative play: it could be configured such that one player would move the character, and the other would aim and fire the pistol. It was a clever enhancement to single-player, and made the game twice as fun. We almost never played alone.
An interesting bug we discovered was that you could shoot, toss grenades, and even search and stick up guards through walls at outside corners. We mostly played on our Atari 800; I've always wondered if the Apple II version behaved the same way.
If anyone is interested, just 'sudo apt install atari800' and get the ROM from atarimania. (Don't be too critical of the controls if you're playing with xbox-style controllers- they're a terrible substitute for Atari joysticks.) Also, be sure to check out the PDF of the original game instructions, which include handy German translations of all the in-game dialog. ;)