XXX mode is dynamic game mode where you collect as many items as possible while on the move, and with random conditions / challenges occurring from time to time.
The mechanic is fairly simple, you can tap on the screen, and the more you hold your finger tapped, the more the sphere will move vertically:
There are a few things to keep keep track of here. The bottom of the screen is where the timer is, as the mode is time limited. Instead of the time bar draining, it increases until it reaches its end and the time is up.
The more items you collect consecutively without hitting any red orbs, the combo will increase, multiplying your score.
Keep an eye out for red hostile looking orbs! They will cancel your combo, stop your momentum and depending on the mission requirements, might fail you a bonus objective.
Power ups can appear during XXX mode and they can range from increasing item score, to magnet powerups which attract all nearby items to you in order to more easily collect them.
During XXX mode, special conditions sometimes trigger. They can range from a gravity shift (where the sphere will normally be attracted to the top of the screen and holding tap will lower it) to specific zones on the screen where items won't grant any score.
In the above screenshot, the greyed out items do not grant any score.
Conditions unlock and trigger as you advance in the game and reach more challenging XXX mode stages.