XP

XP (short for experience) is collected to level up. 
After collecting a certain amount of XP, the player levels up and can pick a new upgrade or synergy out of a random selection of 5 (or 4 when playing on Darkness level 9+). During the level up process, the game pauses and afterwards all enemies are pushed away from the player.
XP can be dropped from enemies: Every Small enemy drops an XP orb worth one XP. Elite enemies drop a chest containing 36 XP (in addition to a Character Upgrade). Bosses do not drop any XP. 
Certain upgrades can increase your XP gain, or trigger special effects when you collect XP orbs:
==Level-up formula==
Required XP to reach the specified level:
Level	Required XP
1-19 	10 * level - 5
20 	16 * level - 8
21-39	13 * level - 6
40-59	16 * level - 8
60+ 	level²
==Table==
The table below lists the amounts of XP required for leveling up.
Category:
Category:Stats