This is a Clock that can add to or subtract from the timer when collected, like in games such as Super Mario 3D Land/World. You can customize the number of timer seconds added/subtracted (from 1-255), the type of effect produced when collected, whether the Clock is solid, and more.
It also handles overflow and underflow - If adding to the timer would take it past 999, the timer is set to 999. If subtracting from it would take it below 0, the timer is set to 0 and the player is killed with a TIME UP!.
The submission has been updated to fix an oversight where if substraction results in exactly 0, the player is left with infinite time, and also made second timing for addition consistent. I didn't find any other issues, so accepted.