A Box counter is an object first featured in Crash Bandicoot 2: Cortex Strikes Back, usually located at the exit of a level. It consists of a three-dimensional hologram of a spinning ? crate, and feature how many boxes have been broken in a level and how many the player should break in order to be awarded a gem. If the box objective is complete, the counter will turn into a gem.
Box counters are kept in Crash Bandicoot 3: Warped and Crash Bandicoot: The Wrath of Cortex, however some non-platforming levels (especially the flying levels) don't feature a box counter as they don't feature an exit either. In these levels the clear gem is acquired automatically as the last box is broken. Levels with two exits may have two box counters as well, Deep Trouble for example.
When all box gems are already obtained on a level, the box counter will no longer appear. An exception to this is in Turtle Woods, where if the player has obtained the box gem but not the blue gem, then the hologram will show that zero boxes must be broken. This is a hint that the player needs to break no boxes to obtain the blue gem.
If the player reaches the end of the levels Hang Eight or Plant Food with time still remaining on the timer, the box counter will be replaced by a special gem and will only reappear if the player re-spawns in a checkpoint.
Box counters return in Crash Bandicoot N. Sane Trilogy where they are featured in the first game also. They function mostly the same as in the original games. However, in Crash Bandicoot, if the player has died in a level where it is possible to get a colored gem, the box counter will show an iron crate instead and it can't turn into a gem.