Some ideas for properties:
- Ball type: This could be for things like Spike Balls, Boulders (they actually damage you, PLUS they are heavy, and will destroy nearly anything in its path - including enemies), Combustible Rolling Balls (they explode when contact is too great).
- Color properties: Go figure.
- Other properties: For things like Ball size, HP until broken, weight type (for the things it can trigger, depending on its weight AND type; pushing certain buttons, intensity of damage toward enemies or the character, rolling speed, etc.).