Anyone know where i should start when it comes to making my draw-line dash attack?

So the idea is that I want to be able to draw a line on a top down 2D space, and when it hits an 'Enemy' or any thing defined as such, it marks that point and chains off once more so it can select another 'Enemy' and finally at the end it dashes through them dealing damage. I'm new to game development and coding in general so I'm not sure exactly where to start. the only thing that is somewhat close to what I'm wanting is with "Tainted Judas" in the Binding of Isaac.