Learn English – What do you call a person who loves to sit in front of the computer

Perhaps hardcore gamer

Someone who plays video games as a primary hobby. They tend to spend large amounts of time playing games, often in excess of two or three hours a day.

There are several possible answers;

If this behavior is intentional - they may be a "saboteur" (one who sabotages), they may be "deceitful" (deceiving or misleading others), "suborning" (inducing (someone) to commit an unlawful act) or "malicious" (intending or intended to do harm).

If it is unintentional - then they are "mistaken" (wrong in one's opinion or judgment), "incorrect" (not in accordance with fact; wrong) or possibly "out-of-date" (no longer useful or acceptable) or even "out of touch" (not keeping informed of the developments relating to someone or something).