More refinement, this time with more impact on the gameplay. For one, the shotgun needs to be reloaded (stand still) and the collected items now also have an effect. Namely a new bullet slot and invincibility.
Adding the reload part is done with the following code piece. If the joystick is not moved and the player isn't waiting for the recoil to end the variable PLAYER_STAND_STILL_TIME is increased. Once it hits 40 frames one shell is added.
;check if player moved
lda $dc00
and #$1f
cmp #$1f
bne .PlayerMoved
;do not reload while recoil
lda PLAYER_SHOT_PAUSE
bne .PlayerMoved
inc PLAYER_STAND_STILL_TIME
lda PLAYER_STAND_STILL_TIME
cmp #40
bne .HandleFire
;reload
lda #1
sta PLAYER_STAND_STILL_TIME
;already fully loaded?
lda PLAYER_SHELLS
cmp PLAYER_SHELLS_MAX
beq .HandleFire
inc PLAYER_SHELLS
;display loaded shells
ldy PLAYER_SHELLS
lda #2
sta SCREEN_COLOR + 23 * 40 + 18,y
lda #7
sta SCREEN_COLOR + 24 * 40 + 18,y
The other addition enhances the PickItem routine. Simply check the picked item type, and either add a new bullet slot or increase the player live counter.
!zone PickItem
PickItem
lda ITEM_ACTIVE,y
cmp #ITEM_BULLET
beq .EffectBullet
cmp #ITEM_HEALTH
beq .EffectHealth
.RemoveItem
lda #ITEM_NONE
sta ITEM_ACTIVE,y
lda #3
jsr IncreaseScore
jsr RemoveItemImage
rts
.EffectBullet
lda PLAYER_SHELLS_MAX
cmp #5
beq .RemoveItem
ldx PLAYER_SHELLS_MAX
lda #224
sta SCREEN_CHAR + 23 * 40 + 19,x
lda #225
sta SCREEN_CHAR + 24 * 40 + 19,x
lda #6
sta SCREEN_COLOR + 23 * 40 + 19,x
sta SCREEN_COLOR + 24 * 40 + 19,x
inc PLAYER_SHELLS_MAX
jmp .RemoveItem
.EffectHealth
lda PLAYER_LIVES
cmp #99
beq .RemoveItem
inc PLAYER_LIVES
sty PARAM1
jsr DisplayLiveNumber
ldy PARAM1
jmp .RemoveItem
