c/app/matrix_rain.c · 6872 字节 · 下载原文

/* matrix_rain.c —— 字符矩阵雨
 * matrix_rain.c — character matrix rain
 *
 * ## 这是什么、为什么自己写
 * ## What this is, and why it is written from scratch
 *
 * 名字最像的那个程序（`cmatrix`）是 **GPL-3.0**（Chris Allegretta 等），
 * The program with the most similar name (`cmatrix`) is **GPL-3.0** (Chris Allegretta et al.),
 * 而 `Examples/` 会随 APK 分发 ⇒ **不能直接收进来**。按本仓既定的那条路走
 * and `Examples/` ships with the APK ⇒ it **cannot simply be taken in**. So we follow the path this repo already established
 * （同 `basic/gorilla.bas`）：**只参考玩法规则，代码自己写** ——
 * (the same as `basic/gorilla.bas`): **reference the gameplay rules only, write the code yourself** —
 * 结构、变量名、注释、函数划分都不抄。
 * the structure, variable names, comments and function split are all our own.
 *
 * "玩法规则"就三条，够描述清楚了：
 * The "gameplay rules" are just three, and that is enough to describe it:
 *   ① 屏幕按列划分，每列有一串往下落的字符；
 *   ① the screen is divided into columns, and each column holds a string of characters falling downward;
 *   ② 串的头部亮、越往后越暗（本平台 conio 只有 16 色，所以用"亮绿 / 暗绿"两档）；
 *   ② the head of a string is bright and it dims toward the back (conio on this platform has only 16 colors, so we use two levels: "bright green / dark green");
 *   ③ 掉出屏幕底部后从顶部重新开始，`kbhit()` 一有按键就结束。
 *   ③ after falling off the bottom it restarts from the top, and `kbhit()` ends the program as soon as a key is pressed.
 *
 * ## 用哪一层画
 * ## Which layer does the drawing
 *
 * 走 `conio.h`（DOS 那套：**坐标 1 起、写完立即上屏**）——
 * It goes through `conio.h` (the DOS set: **coordinates start at 1, and a write reaches the screen immediately**) —
 * 它不需要 `refresh()`，代码最短，也正好压一压"老程序兼容"这条线的另一组接口。
 * it needs no `refresh()`, the code is the shortest, and it conveniently exercises the other group of interfaces on the "old program compatibility" line.
 *
 * ⚠ 坐标必须自己夹在 1..COLS / 1..ROWS 之内：本平台**不做**边界裁剪，
 * ⚠ Coordinates must be clamped to 1..COLS / 1..ROWS by hand: this platform does **no** boundary clipping,
 *   越界写会画到别的行上去（不报错，只是画面花）。
 *   writing out of range lands on another row (no error, just a garbled screen).
 */

#include <conio.h>

#define COLS 80
#define ROWS 25
#define DROPS 40          /* 同时下落的串数 */
/* How many strings fall at the same time */
#define GLYPHS 40         /* 字符集大小：'!' 起往后取 40 个 */
/* Size of the glyph set: take 40 characters starting from '!' */

/* 每条串的状态 */
/* State of each string */
int drop_col[DROPS];
int drop_head[DROPS];    /* 头部所在行（0 = 还没进屏幕） */
/* Row the head is on (0 = not yet on screen) */
int drop_tail[DROPS];    /* 尾巴长度 */
/* Tail length */
int drop_gap[DROPS];     /* 连下几拍（让串有快有慢） */
/* How many ticks in a row it falls (so some strings are fast and some slow) */

/* 自带的伪随机：**不用库里的 `rand`** —— 一来本平台 `rand` 曾长期只有声明没有实现，
   Its own pseudo-random generator: **do not use the library `rand`** — for one thing, `rand` on this platform long had a declaration but no implementation,
   二来自己带一个 LCG 才能保证"同一台机器两次跑起来的序列可复现"（排查画面问题时省事）。
   and for another, carrying our own LCG guarantees that "the sequence repeats across two runs on the same machine" (handy when chasing screen problems). */
unsigned int rng_state = 20260923;
static int rnd(int n)
{
    rng_state = rng_state * 1103515245 + 12345;
    return (int)((rng_state >> 16) % (unsigned int)n);
}

static void drop_reset(int i)
{
    drop_col[i]  = 1 + rnd(COLS);
    drop_head[i] = 0 - rnd(ROWS);      /* 负数 = 还在屏幕上方等着 */
    /* Negative = still waiting above the screen */
    drop_tail[i] = 4 + rnd(10);
    drop_gap[i]  = rnd(3);
}

int main(void)
{
    int i;
    int frame;

    clrscr();
    for (i = 0; i < DROPS; i = i + 1)
        drop_reset(i);

    /* 跑够一段时间就自己收尾（手机上没键盘时不会永远占着） */
    /* It wraps up by itself after a while (so it does not hog the screen forever when a phone has no keyboard) */
    for (frame = 0; frame < 600; frame = frame + 1) {
        if (kbhit())
            break;

        for (i = 0; i < DROPS; i = i + 1) {
            int y;

            if (drop_gap[i] > 0) {          /* 这一拍不落 */
            /* No fall on this tick */
                drop_gap[i] = drop_gap[i] - 1;
                continue;
            }
            drop_gap[i] = rnd(3);

            /* 把尾巴最上面那一格擦掉 */
            /* Erase the topmost cell of the tail */
            y = drop_head[i] - drop_tail[i];
            if (y >= 1 && y <= ROWS) {
                gotoxy(drop_col[i], y);
                textcolor(2);               /* 暗绿 */
                /* Dark green */
                putch(' ');
            }

            /* 头部先降一格再画：留下来的是"尾"，正在画的是"头" */
            /* Lower the head one row before drawing: what stays behind is the "tail", what is being drawn is the "head" */
            drop_head[i] = drop_head[i] + 1;

            /* 上一格由"头"变成"尾"：重画成暗绿 */
            /* The previous cell turns from "head" into "tail": redraw it in dark green */
            y = drop_head[i] - 1;
            if (y >= 1 && y <= ROWS) {
                gotoxy(drop_col[i], y);
                textcolor(2);
                putch(33 + rnd(GLYPHS));
            }

            /* 新的头：亮绿 */
            /* The new head: bright green */
            y = drop_head[i];
            if (y >= 1 && y <= ROWS) {
                gotoxy(drop_col[i], y);
                textcolor(10);              /* 亮绿 */
                /* Bright green */
                putch(33 + rnd(GLYPHS));
            }

            if (drop_head[i] - drop_tail[i] > ROWS)
                drop_reset(i);
        }
    }

    /* 收尾：恢复默认配色并把光标放到最后一行的行首，别把终端留在半截状态 */
    /* Wrap up: restore the default colors and put the cursor at the start of the last line, so the terminal is not left half-done */
    gotoxy(1, ROWS);
    textcolor(7);
    return 0;
}