Interrupts

Interrupts are a facility for modifying the rendering process. The renderer takes the scene's components (field, palette, scroll, etc) and combines them to produce an RGB buffer for the display. Conceptually, it does this by starting from the top of the display and working its way down, line by line. Interrupts let you inject customizations into this process. An interrupt does this by targetting a specific y position, called a "scanline", and then trigger an "irq" function. This function is able to modify any component however it wishes, which will then affect the remainder of rendering.

Interrupts are great for creating parallax effects, wavy background motions such as flames or heat waves, water margins, and similar effects.