More Demos and Movement

Entry posted by arwanderer in Programming September 15, 2023

373 views

On Sunday evening, I worked through the NUSIZx and Missile demos and finally the playfield on Tuesday before moving on to Chapter 3: Movement.

I didn't have too much difficulty with the last demos in the graphics chapter and only had a few errors to correct each time before the program compiled correctly. In Chapter 3, however, I am having some issues. The ship sprite is not positioned correctly and, when it moves, it messes up the screen. I've compared my code to the original several times, but still haven't pinpointed the exact problem.

movementdemo.jpg.d460f72c19cf2f3ecdcd73c6f45acd62.jpg

UPDATE+++

After having another look at the code, I discovered that, ONCE AGAIN, I had typed "LDA" where an "LDX" should have been! Here's what the fixed code looks like and where the problem was:

LDA XPOS

LDX #0

JSR x_position

LDA XPOS2

LDX #1

JSR x_position

I'll have to pay more attention to this. After making the changes, the program compiled and ran properly and smoothly on the emulator without issue. Chapter 3 is complete, but I'm going to re-read it before moving onto Chapter 4: The Sound of Fun.