diff options
Diffstat (limited to 'src/enemies.s')
| -rw-r--r-- | src/enemies.s | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/enemies.s b/src/enemies.s index facb255..7097af5 100644 --- a/src/enemies.s +++ b/src/enemies.s @@ -613,7 +613,16 @@ .endproc ;; The enemy has been set to dust, remove it. + ;; + ;; NOTE: the 'x' register is modified, the 'y' register is _preserved_. .proc bite_the_dust + ;; This function might be called by loops which abuse index + ;; registers. Luckily that's not the case for the 'x' register, but at + ;; least the loop on Bullets::update() does heavy use of the 'y' + ;; register. Preserve it now on the stack. + tya + pha + ;; Invalidate this enemy. lda #$FF ldx Enemies::zp_pool_index @@ -634,6 +643,10 @@ ldx Enemies::zp_pool_index sta Enemies::zp_enemies_pool_base + 3, x + ;; Restore back the value for the 'y' register. + pla + tay + rts .endproc |