It might be that the texture filter is "linear" instead of "nearest", if you used Godot to make your game you can go to Project Settings and in texture you can change "default texture filter" to nearest: what this does is that when displaying an image with pixels bigger than 1x1 (for example, if you scale an image), for each actual pixel on the screen, instead of picking a color in between the colors of the two nearest pixels it will chose the exact color of the nearest pixel (I might not have explained very well but that's my understanding of it)