There was something magical about the old video game cartridge.
The satisfying "thunk" of sliding it home into the cartridge slot. The stack of grey plastic blocks you'd balance beside your beloved console. The peculiar ritual of blowing into them if they stopped working ("You've got to get rid of the dust").
But what was actually inside that brick of plastic?
The size of each game's internals would vary hugely: the game shown above only required a small amount of "hardware" to sit inside the cartridge, from programmable ROM chips to pin connectors.
If a game had more hours of content to play through (think any of the Zelda titles), it would use a great deal more space inside the cartridge - but simpler titles would use comparatively little space.
Now you know.