Title: Sensitive
Developer: Oliver Kirwa
Publisher: N/A - public domain
Year: Unknown, but something buried deep within the code mentions 1989/1990
Platforms: Commodore 64, Commodore Plus/4
Genre: Puzzle
Players: One player only

Sensitive is a very fun little puzzle game, and a shining example of entertainment that wasn't made for profit.

The concept is very simple: you play a blue dot, which you have to guide with the joystick to the exit. The whole screen is a grid of tiles, and you have to make all of the tiles capable of exploding do so before the exit becomes active.

Types of tiles:

Blue and black stripes
This is the background. If you touch it, you lose a life.
You need to get to this, but only after all the tiles that can explode have done.
Plain grey
You can rest safely here. They don't explode.
Yellow and grey stripes
These explode as soon as you touch them, so move over them very quickly.
Animating yellow and grey stripes
These take longer to explode so either stay on them for a short while, or move off them then back onto them again.
Grey with a dark grey line
You can only move across these in the direction of the line, which is either horizontal or vertical. You can safely rest on them.
Grey with a white 'T' letter
Teleport. Press the fire button to move to another teleport tile.

The upside down pyramid level appears to be impossible. If anyone has any information on this, please let me know!

If you ever have the time and inclination, it's well worth the 12KB the file takes up in my opinion. I can only hope that one day someone will write a free version for a modern platform, preferably with a construction kit to design your own levels. Games as good and simple as this are somewhat rare.