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Writing a NES game day 11, Fire!

Now that I have my first version of the character, and he can move, I need to make him so something else. Remember that you can check the status of the code in my github repo.
I created a simple sprite for bullet which is a 2 colors circle (redoing sprites into something better is a problem for future me) and created 3 variables for this: sx (shoot in x axis), sy (shoot in y axis) for the position of the shoot every frame and a shootStatus to see if it is actually firing something or not (maybe in the future I can delete this variable and use a special value in sx and clean 1 byte?)
For making this work, I added the shoot behaviour to button B in the engine sector:

    CMP #%01000000
    BNE bDone
    LDA #$01
    STA shootStatus
    LDA p2x
    STA sx
    LDA p1y
    STA sy

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After that, I see if the shooting is active and I jump to a shooting "function"

;Shooting update
LDA #$01
CMP shootStatus
BNE :+
JMP shoot
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And then the shoot part:

    ;for now it will only shoot to the right.
    LDA sx
    ADC #01
    STA sx
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As you can see I place a lot of comments, the code in assembly is not that "self readable" as other languages.

Now, I have to update the sprites refresh to make all this visible.

LDA sy
    STA $0210
    LDA sx
    STA $0213
    LDA #$00
    STA $0212
    LDA #$01
    CMP shootStatus
    BEQ isShooting
    LDA #$FC
    STA $0211
    JMP shootDone
    LDA #$30
    STA $0211
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As it is a one tile sprite, I only need 4 positions in memory, so I assigned it the $0210 to $0213 space.

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(tomorrow we will talk about the other thing that appears on the screen)

On the other hand, to keep me MORE motivated I am playing some nes games lately. Not only Final Fantasy in japanese to learn, but I started Rockman (Megaman)

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If you have a child that loves video games, show them the old Nintendo games, for them this all will be in nightmare level.

Top comments (2)

michaeltharrington profile image
Michael Tharrington

Loving this series!! 🔥

sreno77 profile image
Scott Reno

You're making progress. Keep going!