Developing NES games with C language (cc65) 10. Game cycle

Paste the CSDN The format is not adjusted , If you want to see a good format, click below

https://happysoul.github.io/nes/nesdoug/

 

Let's talk about the game cycle

The game needs a cycle ,while(1){}

 

The first item in the cycle is ppu_wait_nmi(), He will wait for the start of a new frame to trigger nmi, Per second 60 frame （ European version is 50 frame ）

however , If the logic of the game is too complex, it will take more time , And more than nmi Start of trigger , Then wait until ppu_wait_nmi() after , He will wait for the next frame , This will make the game slow .

Fortunately, this has not happened yet , Because our code is too short , But the later game is not so simple , So we should pay attention to the simplicity of the code .

 

The controller uses

pad_poll(0)

get_pad_new(0)

 

Then I want to say clear_vram_buffer(), These codes are unique to me . because nmi The role of , We need to rewrite him , So that he can achieve more functions

score_lives_draw() Use one_vram_buffer() Redisplay the scoreboard at the top of the screen .

These similar vram_put(), But they will be put in the buffer , also nmi The code will be v-blank Automatically push them to ppu.

 

 

Then there is the logic of the game , Mobile racket , Moving ball , Check for collisions .

Moving handle

 

 

if(pad1 & PAD_LEFT){

Paddle.X -= 2;

if(Paddle.X < PADDLE_MIN) Paddle.X = PADDLE_MIN;

}

if(pad1 & PAD_RIGHT){

Paddle.X += 2;

if(Paddle.X > PADDLE_MAX) Paddle.X = PADDLE_MAX;

}

 

 

 

Moving ball , If he is mobile

 

 

if(ball_direction == GOING_UP){

Ball.Y -= 3;

if(Ball.Y < MAX_UP){

ball_direction = GOING_DOWN;

}

}

else { // going down

Ball.Y += 3;

if(Ball.Y > MAX_DOWN){

--lives01;

ball_state = BALL_OFF;

}

}

 

 

 

Then came the drawing wizard , First, clean up the old , Then redraw all active sprites .

 

If a piece is hit by the ball ,hit_block(), Delete this block from the collision graph , Fill this area with a blank block .

Again , I use vram The buffer temporarily stores it , And in v-blank Automatically send it to PPU.

 

Usually , I will use many

game_states： Such as the title , game , Pause , end .

I use different ball_states： Fly out of the screen BALL_OFF, Prepare to launch the ball BALL_STUCK ( Stuck on the edge of the plate ), The ball is moving BALL_ACTIVE

 

I use NES Screen Tool Production background , stay c1.csv Blocks that can be destroyed are defined in . I'm useless Tiled Tools , Because he shows easily , However, if the corresponding destructible block layout is modified, it also needs to be modified （ That's the front one c1.csv）

 

 

 

const unsigned char c1 [] = {

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,

0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,

0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,

0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,

0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,

0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,

 

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

};

 

 

 

Use grey bricks in NES Screen Tool Chinese painting , Then compress the export RLE file .

 

 

I am here NES Screen Tool The property sheet has been changed in advance , Then save the background . This is the color of the tiles , They are different palettes . But they all use the same tiles . This is the property inspector view （ Press “A”）.

 

 

The scoreboard will be updated every frame , Please note that I save each number of scores as a separate variable （ Grade is 0-9）

score10 yes 10 digit ,score01 It's a single digit . because 6502 The processor lacks built-in mathematical operations , So division and modulus pair NES The operation of is very slow , So keeping each number separate can speed up the code .

 

 

https://github.com/nesdoug/12_Break

 

Now it's easy to turn this into a game , But horizontal movement requires complex code , I will write the example as simple as possible .