This battle is fought on a looped circuit. Here, Sonic and Shadow must race each other to gain Energy Cores. During the race, Shadow will use his own version of the Boost when Sonic gets ahead of him or activate his own Boost. Should each character collide while boosting, they will ricochet to the left and right. There are certain parts of the arena where Shadow will slow down to collect Rings and maintain his boost, during which the player can hurt him with the Homing Attack or Boost. However, it is not advised to attack Shadow when he and the player are close to the Energy core, as that may launch Shadow directly at it.
There are certain sections on the circuit that both the player and Shadow can take advantage of; between the straight paths on the circuit, there will be sharp corners where the player will have a hard time collecting the Energy Core if they do not use the Drift or Boost. Also, before the section leading to the starting point of this circuit, there is a wavy plateau that only the player can access by alternate paths, giving them the chance to take the Energy Core without opposition. It should be noted that on the final stretch on this circuit before returning to its starting point, the Energy Core cannot be collected. Instead, it will stop floating and vanish until the player passes the starting point for the circuit again.
During the race, the player can pick up Rings, destroy blue-tinted Meteorites and utilize Trick Jump Panels to keep the Boost Gauge filled. During the course, should Sonic fall too far behind Shadow, Shadow will fire several damage-inducing Chaos Spears directly at him. Once either Sonic or Shadow gain two Energy Cores, they will immediately perform a special attack. If Shadow gains two Energy Cores first, he will launch several Chaos Spears onto the ground that Sonic will have to avoid using Quick Step, before launching a large Chaos Spear at Sonic (while applying Chaos Control) to throw off Sonic's timing. If Sonic gains two Energy Cores first, he will automatically use a powered-up Boost which lets him smash into purple Meteorites that will fly into Shadow, slowing him down. If Sonic can catch up to Shadow, he can ram into Shadow, eating away at his rings. The battle ends when either character loses all their Rings.
In hard mode, both characters have to get three Energy Cores in order to perform their special attacks. Shadow also seems to be much faster and more proficient in pursuing Energy Cores, taking the higher routes more often. The blue meteors and almost every trick ramp that give boost energy are also absent, making it harder to maintain boost.
In the Nintendo 3DS version, Shadow has three attacks: Chaos Spear, Chaos Control/Boost and the Homing Attack. Every time Sonic gets ahead of him, Shadow will use his Boost to catch up, which is faster than Sonic's boost and as a result it could end in Shadow running over Sonic. If Shadow is ahead of Sonic, he will start throwing him Chaos Spears and if the hedgehogs are really close to each other, Shadow will try to homing attack Sonic. Sonic can hit Shadow with either the boost, the Slide Attack or the Stomp.
The main stage theme music is a remix of "For True Story" from Sonic Adventure 2. During the stage when using the default music, the music switches to "Live and Learn" if Sonic gains two Energy Cores. If Shadow gains two Energy Cores, the music switches to the Crush 40 version of "All Hail Shadow". After about 40 seconds, the music returns to "For True Story".
When Sonic powers up, his boost changes color from cyan to purple.
However, there is a minor difference: In the original, the entire side of the moon (that the camera is pointing at) is light, but in Sonic Generations, one half is light, and the other side is dark. (This is also the side Shadow is on when he jumps)
This version of the fight takes place on a looping arena with many interactive objects such as grind rails and meteorites, which differs greatly from the original, which took place in a never-ending straight track, with no rails and meteorites as merely destructible objects
Perhaps the largest change in the structure of the course is the fact that the platforms do not disintegrate as Sonic runs on them, as they did in the original.
This is the only Rival Battle where the Rival is governed by rings rather than a set amount of hits emphasizing the race aspect to defeat one another rather than a straight out battle.
Shadow is the only rival boss who does not skid across the road after he takes damage.
This is the only boss that never switches to 2D gameplay.
When Shadow runs into the trick ramp, he does one Trick Action and a round kick, then falls to the ground.
Before the race, it's shown that Shadow guards the fourth Chaos Emerald. Although this is just due to his position as a boss (both chronologically and in order), this ends up as a coincidental reference to a famous line from Shadow the Hedgehog, where Shadow says: "Where's that DAMN fourth Chaos Emerald?".
This is the only rival boss that does not take place in the future.
If one manages to leave the area where Shadow unleashes his special move, his AI will have problems. He'd knock into walls and reach ridiculous speeds that even the Sonic Boost can't keep up with. If the player stays at the area with the Rainbow Ramp long enough, he'll unleash a Chaos Spear that will mute the whole game. The sound would be restored after reloading the game. Also, Power Cores will not appear on the stage game so whenever the player activates this glitch so the player will need to restart or exit the stage.
If you get the second energy core as you are doing tricks, the models for Shadow and the asteroids will disappear for the rest of the fight.
If Sonic, from the area where Shadow uses his power-up, runs a long distance until the path ends in a pit where Sonic falls to his death and loses a life.
If Sonic were to run the track backwards while Shadow goes forwards, Shadow will gain energy cores much faster.
Though hard to catch glimpse of, Shadow can be seen charging his Chaos Spear attack while running if Sonic stays behind him (not too far, but close by, otherwise Shadow will launch them).
"Rival Battle: Shadow the Hedgehog" "For True Story (Short ver.) - Circuit Freq RMX"