How does your submission match the theme?
Summary (expanded explanation follows after)
We make dual use of shooting (move and shoot)
We make quadruple use of the shots (enemy, ammo, points, and incentive to move (both because it fades, and because it slows you down))
We also make dual use of the player (the player creates what challenges and is also the player who must overcome said challanges)

Explanation:
"A good idea solves multiple problems"

We generate no enemies, no obstacles, in a completely cyclical game world where momentum is maintained.

The player is fading to black, if he becomes completely black he dies
To become white he must shoot or collect points

Shooting is the players only way of movement (from the recoil).

Shots start off red and will kill the player if he does not dodge them (dodging them will create more shots he will need to later dodge).

After a bit of time, the shots change color to blue and become points the player needs to collect (because they give the player both points and more ammo with which to shoot).

To collect these points/ammo he will need to move towards the blue shots, because if he waits to long they disappear, and he might run out of ammo.

Also because picking up ammo counts as a collision you lose some of your momentum and might need to shoot to maintain your ability to dodge shots at a lower cost

Of course moving at a reckless speed makes it harder for you to dodge because of how fast the "level" is shifting, but it can save you ammo, so...
In short, we create a feedback loop for the player where everything you do leads you to doing everything else, endlessly.

Special note : The game is EXTREMELY MINIMAL.

Third-party resources
Unity Game Engine
Unity Standard Assets

Contributors
Daniel Peres: Design, Programming
Yaron Gur-Arieh: Programming, Design