Growth

I was only a little kid when I first played it.

A simple, small, obscure, old Amiga game.

Also, one of the most important learning experiences of my life.

The game is a hybrid of Breakout and Space Zap (reversed), in which you have to destroy the core of the "growth" by shooting through a constantly increasing amount of matter.

If it reaches the edges of the screen, you lose; you have to pay attention and prevent it from expanding too much.