Metal Gear Solid Portable Ops Plus does not contain the single-player campaign that is in Metal Gear Solid: Portable Ops. Instead, PO Plus has a whole new single-player mode entitled "Infinity Mission" that offers nothing in regards to the storyline of the Metal Gear series. Players who have saved information on their PlayStation Portable from Portable Ops can carry over their saved data and use the same character roster in PO Plus.
Infinity Mission has Easy, Normal, Hard and Extreme difficulties. Your troops are divided into two groups during the Infinity Mission: Sneaking Team and the Truck Team, the Sneaking Team consists of the four active characters (i.e. Naked Snake, Gene, Null and Python) whereas the Truck Team consists of any troops you recruit during the missions; they are interchangable and can be switched around at any time.
The solo mission is split into a series of stages that must be completed before players are able to permenantly save data. Most stages have the same objective: Reach the goal to clear the stage to move onto the next stage, some however require the player to fulfill certain objectives such as staying alive until the timer runs our and the final stage in each round has the player eliminating a certain number of foes (depending on difficulty). Each mission enables the player to recruit any soldier they come across, much like in Portable Ops, and after each successful stage both the Sneaking Team and the soldiers inside of the truck recieve experience points.
New additions to Portable Ops Plus include:
- Textbooks: Items which can be used to boost soldiers skills, they can be used once and only if a soldier hasn't already reached the maximum level for that skill (indicated by a white arrow)
- Fulton: A means of ejection, finding a fulton allows the player to eject from a mission and keep all soldiers, experience points and weapons they acquired
- Stealth: Whilst not new, stealth camouflage can now be found randomly whilst in a stage
Portable Ops Plus feels more like an expansion pack than a sequel with nothing added to the story in PO. The main selling point is that there are more online modes for players to indulge themselves and a few new charaters to unlock from other Metal Gear games.