Mayhem Mode

Mayhem Mode is one of four (Version 1.3.4) or six (Version 1.4.0) Game Modes, along with Zen Mode, Training Mode, and the Local Multiplayer modes. It's description in the mode menu is "boss challenge."

Obstacles
Mayhem increases and the speed of the game. There is also a twist. Before you enter the next checkpoint, there is a Boss. You can't enter the next area unless you have defeated it.

Types
There are three types of bosses in this mode, specifically the 1x1 boss, 3x1 boss, and the Cross-Shaped boss. Bosses can appear together (multiple) on certain checkpoints.

Crystals
Every checkpoint (except for Endless Mode) has a boss at the end of it. Prior to the boss battle, players are often given a few crystals to help prepare them for the upcoming boss(es), with a few exceptions. Checkpoints that usually end as Break Points (many crystals) don't give players the bonus of more crystals prior to the battle.

Defeat
To defeat a boss, players must destroy all of the glass panes on the boss. Keep in mind that the cannon the boss uses doesn't count as a pane, so attempting to destroy that will not get you anywhere.

1x1 bosses are the simplest to defeat, with only 5 sides to hit, while the Cross-Shaped boss is the hardest; requiring players to hit 21 panes. Some bosses also use levitating glass panes as shields.

Fighting back
Bosses will also fight back, as they are equipped with cannons to fire small cubes of glass at players. When firing, the boss will tend to move backwards, away from the player, and their cannon will glow. Usually, the weaker bosses will fire more, but that's not always the case. If a boss has a ring of glass panes defending it, they will move below the boss, opening the boss's line of sight. It also avoids destroying its own armor.

Color
The checkpoints in Mayhem are given a red, more sinister tone as well. It is highly recommended that players reach the Endless Mode in Classic before attempting Mayhem. The boss stage's color depends on the last stage of the checkpoint, as the color is derived from that last stage (with the exception of Checkpoint 11).

Version 1.3.0
It sounds like a Dubstep Remix of Smash Hit Menu Theme

Version 1.3.4
In the Version 1.3.4 of the Game, the Mayhem Mode Menu Theme was changed and it sounds like a Trap Remix version of Smash Hit Menu Theme. It's noticeable at the end