Key and Lock

---

This example shows how to make an adventure game where the player has to collect keys in order to unlock doors.  There is an object that displays the number of keys above the player sprite.  When the player object collides with the lock object, there is a check to see if the player has at least one key.  If so, one key is subtracted from the total, and the lock object is destroyed.  Also, a sound plays when the player collects a key, and when the player unlocks a lock.