What is the genre of this type of 2D game:
The unit controlled by the player (blue) tries to cross the stage without getting hit by the enemies (red). If the player succeeds, any area without units (the left side in the example) becomes solid?
The goal of the game is to fill out the biggest area possible without getting hit.
I remember seeing several clones of this game a long time ago, but can't get the right search keywords to find any of them.
These sorts of games are either direct clones of, or based off the mechanics of a game called Qix, a puzzle game originally released in arcades. Therefore, "Arcade puzzle game" would be the appropriate (but not very useful) genre.
A more useful definition might be "Qix Clone" or "Qix-like" - these are the terms you probably want to search by if you're looking for games with the same or similar mechanics of the original.
Note that some Qix-like games may alter the gameplay somewhat, while maintaining the core mechanic of enclosing areas and not getting hit. Frenzy (1984), for example - enclosing an area will capture (remove) enemy units instead. Removing all enemies OR enclosing 95% of the board will complete the level.
I am unfortunately obliged to give a content warning: some of the cheaper/modern versions of Qix have an erotica component, where enclosing areas of the board reveals a risque picture underneath. Just something to bear in mind.
