The phrase "normal difficulty" is correct and commonly used in written English.
It is usually used to refer to a level or degree of difficulty that is considered typical or expected. Example: The math test was challenging, but it was within the normal difficulty range for our class.
XCOM 2 is a serious strategy game, even on normal difficulty.
On a 'Normal' difficulty level rivals will offer absolutely no contest, and you'll rarely lose.
It took me about 14 hours of solid play to get through the single-player story in Uncharted 2 on normal difficulty.
These enemies rough-house the player on even "normal" difficulty but, once the setting is at Master Ninja, they attack relentlessly with brutal health-chewing grabs and projectiles.
The guards of Dishonored, at least on the normal difficulty setting, are astonishingly stupid, chalking up mysterious sounds to rats when they know an assassin has been methodically taking out their employers.
When I first began the 28 hours I spent getting through StarCraft II's main single-player campaign on normal difficulty, I was shocked time and again at the depth and care in the game's production quality.
In deference to this complexity, the D.S.M. cautions users against taking too literally the sharp boundaries between disorders and between illness and the normal difficulties of life.
From this perspective students can then make realistic life changes and build the internal skills which will enable them to develop the emotional resilience required to face the normal difficulties and challenges of life.
Not only is the font set comically large (it's funny because it's true) but she has the normal difficulties using an iPhone that anyone who lived through Watergate does.
Normal difficulties with public speaking or test-taking suddenly become a focus of concern.
And we had to fight that battle over and above all the myriad "normal" difficulties that all graduate students faced.
