Designing Power-Up Mechanics!
The details of power-ups, like many game elements, need to be fine-tuned by trial-and-error. The “right” settings are different for every project and power-up.
Consider a game like this:
An additional enemy is spawned every 2–3 seconds, and a power-up every 6–17 seconds.
It should give a quick boost for a few seconds, just enough to get out of a tight spot using 3x player movement speed. I’ve given it a duration of 3 seconds.
Shoot 3 lasers instead of 1 for a limited time. Increases your capacity to kill enemies by a generally small amount unless paired with Speed boost. Has a 4-second duration.
A powerful power-up that can protect the player from a single fatal collision. The shield expires after either protecting from a collision OR after 6 seconds.
All this means there is currently a MAXIMUM of 14 seconds and a MINIMUM of exactly 0 seconds where the player has no power-up and, one is not currently available in the level. I’d say that’s a pretty good balance for the current game feel.