How can I create top down mouse-driven aiming? (Crosshair follows cursor, fires projectiles at cursor location)

Have you tried using Draw Texture Simple? Draw Texture is more complex, but gives you more control.

Draw Texture Simple

simply needs the Texture, X & Y location provided by the Setup Above.

Draw Texture

needs the Texture, X & Y, Screen W & Screen H sets Width & Height, Texture U & V can be ignored, but this moves Top Left origin in UV Space, Texture UWidth & VHeight are the scale in relation to the Width & Height, Set these to 1 usually, Blend Mode can be changed to what you desire.

Draw Texture Explained


To further elaborate the uses for Draw Texture. Texture U & V allow setting the Top Left Draw Point of Texture. So if you were using a sprite sheet or any texture with multiple Images. You would set this to start in a position within the texture, then set the Screen W & H to draw the size of the image within that area. UWidth & VHeight could be used to Tile the texture. This tells the texture spaces within the UV. Does it have 1, 2, or 3 spaces? Setting it to 2 / 2 will have the texture repeat 4 times within the given Width & Height aka UV Space. 2 / 1 will print 2, but stretch it horizontally to fill the UV Space.