I built Tictactoe in Excel by creating every possible board state and then hyperlinking between them. I fixed the window size to 3x3 so the window would scroll to each state. Later learned AppleScript to automate parts of this process and eventually got in to HTML.
I feel obligated to note here that PowerPoint is Turing complete. It's pretty radical.
Same here! I had a basic game where an enemy moved across the screen towards the character and you had to shoot it. Clicking the enemy would hyperlink to a slide where you shoot the enemy, the enemies animation finishing (when it touches the character) would link to a slide where you died. Working out how to do conditional logic in PowerPoint at 11 opened up a lot of exciting ideas for PowerPoint games for me. Though it lead to a lot of slides…