In MSCC, the patch automatically makes each level in a game session start with the "full first second", regardless of prior play. This will also eliminate the Long First Second Glitch from long play sessions. Note that resetting the level bonus by going to other levels is still required. In addition to this, Fullsec will manually switch between odd and even step when the F5 key is pressed, similar to Tile World's "O" key. Previously, MS users that wanted to switch between the two modes had to either guess, or go to a different level and then return to the desired level on specific odd or even seconds. Alternatively, there was the option of closing and re-opening the game; but not only was this more of a hassle, but it also only worked reliably for setting even step, the default step parity when the game is opened fresh.
One notable disadvantage compared to Tile World is that feedback as to which mode is being used at the current time is significantly more difficult to access. Tile World displays "odd" on the right hand side of the screen when odd step is selected, whereas there is no such signal on the MS data screen; the only way to find out is to pull up the Best Times menu and read the sentence "You have completed X levels". If odd step is active, Fullsec alters this sentence such that the U in the word You is capitalized. A session will always begin in even step, so this will not be necessary at the beginning of a session where even step is used.
An emerging use of Fullsec is in the making of AVIs; Fullsec drastically cuts down the time required to make AVIs of levels which require a specific odd and even step initialization, with random elements or heavy boosting, or levels that otherwise take many attempts to solve. Fullsec may also see these uses in normal play for endurance runs through extremely unlikely routes, such as Blobnet and Monster Lab.
While it might appear that Fullsec could cause some legality issues for scorekeeping purposes, ccexplore states that "fullsec.exe's patches are guaranteed not to have any impact on the game logic". The timer is not manipulated in any way, and odd and even step can otherwise be obtained normally.