atari2600land's Blog

To make something keep moving in the last direction you need to use "movement deltas". Lets say you have the following variables :-

 

shipX - the ship sprite's X position on screen

shipY - the ship sprite's Y position on screen

deltaX - the ship sprite's movement direction in X

deltaY - the ship sprite's movement direction in Y

 

Initialise deltaX and deltaY to zero outside the main game loop

If you detect left on the stick then make deltaX equal to -1

If you detect right on the stick then make deltaX equal to +1

If you detect up on the stick then make deltaY equal to -1

If you detect down on the stick then make deltaY equal to +1

If you detect no stick activity then don't change deltaX or deltaY

 

You might have to swap up for down above because I'm not sure if the G7000 starts Y at zero from the top or the bottom of the screen.

 

After that just do (in pseudo code) :-

 

shipX=shipX+deltaX

shipY=shipY+deltaY

 

Then the ship sprite will always move in the last direction the stick was in including the diagonals.

Why does everyone use psuedo code on me? I'm still new to assembly so I need actual code to get anywhere to learning things.

Thanks for the info, though.

Why does everyone use psuedo code on me? I'm still new to assembly so I need actual code to get anywhere to learning things.

 

Conversion from pseudo code (or batari basic for that matter) to your machine of choice is a handy skill to have. Once you have things like "if/then/else" down in assembly language you are well on the way to doing interesting things.