Experience Point

Experience Points, or EXP and XP for short, is a unit of measurement used in the Sonic the Hedgehog series.

Description
The main use of EXP is to quantify a player character's progression through the game. Experience points are generally awarded for the completion of missions, killing enemies, and collecting Chaos Orbs. When the player gets enough EXP, they will level up, granting them various boosts to their abilities and granting all-new abilities as well. With each level up, the player needs to collect even more EXP than before for the next level up.

Sonic Adventure series
In the Sonic Adventure series, EXP is used only by Chao who are being raised in the Chao Garden. This EXP is used to level up the Chao’s various stats (Swim, Run, Fly, Power, and Stamina) in order to make them more versatile and skilled in Chao Karate and Chao Racing.

Sonic and the Secret Rings
In Sonic and the Secret Rings, EXP is used as a means of improving the base abilities of Sonic the Hedgehog. EXP is gained by playing the stages or their various missions. EXP is gained in through various methods, including, but not limited to: killing enemies, collecting rings, and finishing missions quickly. when the player

When leveling up through EXP, the player gradually is given new abilities that they can equip to Sonic to improve his performance and skills. Some of these skills also make it easier for Sonic to gain even more EXP, such as the Expert Drift skill, which grants the player bonus experience when turning a corner.

Sonic Unleashed
In Sonic Unleashed, the player needs to collect either Chaos Orbs (PS3/XBox360 version) or red Dark Gaia Force (PS2/Wii version). Regardless of which one, the player can obtain these objects by killing enemies or breaking enviormental objects such as jars.

EXP can be used to empower Sonic manually, both in his normal form and as the Werehog.

In his normal form, Sonic only has two elements that can be upgraded; his speed, which, when leveled up, will increase the top speed that Sonic can reach. The other element is his Ring Energy, which increases Sonic's Boost Gauge limit.

As the Werehog, Sonic makes much better use of the Chaos Orbs/Dark Gaia Force, as he has many more elements that can be upgraded. The first is Combat, which increases the varierty in the Werehog's fighting style. The next is Strength, which increases the power of his attacks, allowing him to eat away at enemies' health faster. Following that is Life, which increases the Health Gauge of the Werehog, allowing him to take more damage without dying. After that is Unleash , which increases the length of the Unleashed Gauge, allowing the Unleashed Mode to last longer. The final element is the Shield, which increases the power and durability of the shield, allowing the Werehog to block stronger attacks as well as last longer against consecutive attacks.

Sonic Chronicles: The Dark Brotherhood
As per most traditional RPGs, Sonic Chronicles features experience points in a manner similar to most other RPGs. The manner in gaining EXP is also the same, as the player gains varying amounts of EXP after each battle, dpending on how powerful the enemies are. When leveling up, the characters' Speed, Attack, Defense, Luck, HP, and PP are all given increases. The player can then also choose one of the above to give an extra point to. Leveling up also improves the character's special skill.

Sonic and the Black Knight
In Sonic and the Black Knight, EXP is referred to as Followers, are representined by villagers of camelot, symbolizing Sonic gaining the trust and loyalty of those living in Camelot. Unlike it's sequel, leveling up with EXP does not provide the player with skills to equip at will. Instead, these skills are granted instantly to the player. Despite being able to gain followers when playing as the Knights of the Round Table, only Sonic himself is affected by the followers when leveling up, as the Knights' skills are instead modified by improving their arsenal of weapons.