From 070e393b7535937a32c6eb1aec674c0187eab761 Mon Sep 17 00:00:00 2001
From: Reiner Herrmann <reiner@reiner-h.de>
Date: Sat, 16 Jan 2021 22:16:19 +0100
Subject: Add initial game

---
 src/main.c | 147 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 src/main.c

diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..30cd2be
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,147 @@
+#include <conio.h>
+#include <stdio.h>
+#include <c64.h>
+#include <joystick.h>
+#include <stdint.h>
+
+struct screen {
+	unsigned char grid[25][40];
+};
+
+enum direction {
+	UP,
+	DOWN,
+	LEFT,
+	RIGHT,
+};
+
+struct player {
+	char x;
+	char y;
+	enum direction dir;
+	unsigned char joy;
+	unsigned char prev_joy;
+	unsigned char next_char;
+};
+
+#define SCREEN (*(struct screen*) 0x0400)
+#define SCREEN_AT(x, y) (SCREEN.grid[y][x])
+
+#define MAX_PLAYERS 2
+
+#define EMPTY  '\x20'
+#define PLAYER '\x71'
+
+#define CHR_V  '\x42'+128
+#define CHR_H  '\x43'+128
+
+#define CHR_DR '\xed'+128
+#define CHR_RD '\xee'+128
+#define CHR_UR '\xf0'+128
+#define CHR_RU '\xfd'+128
+
+static void update_player(struct player *p) {
+	/* has direction been changed? */
+	if (p->joy == p->prev_joy) {
+		if (p->dir == DOWN || p->dir == UP) {
+			p->next_char = CHR_V;
+		} else if (p->dir == LEFT || p->dir == RIGHT) {
+			p->next_char = CHR_H;
+		}
+		return;
+	}
+
+	if (JOY_UP(p->joy) && p->dir != DOWN) {
+		switch (p->dir) {
+			case RIGHT: p->next_char = CHR_RU; break;
+			case LEFT:  p->next_char = CHR_DR; break;
+		}
+		p->dir = UP;
+	} else if (JOY_DOWN(p->joy) && p->dir != UP) {
+		switch (p->dir) {
+			case RIGHT: p->next_char = CHR_RD; break;
+			case LEFT:  p->next_char = CHR_UR; break;
+		}
+		p->dir = DOWN;
+	} else if (JOY_LEFT(p->joy) && p->dir != RIGHT) {
+		switch (p->dir) {
+			case UP:   p->next_char = CHR_RD; break;
+			case DOWN: p->next_char = CHR_RU; break;
+		}
+		p->dir = LEFT;
+	} else if (JOY_RIGHT(p->joy) && p->dir != LEFT) {
+		switch (p->dir) {
+			case UP:   p->next_char = CHR_UR; break;
+			case DOWN: p->next_char = CHR_DR; break;
+		}
+		p->dir = RIGHT;
+	}
+	p->prev_joy = p->joy;
+}
+
+static char move_player(struct player *p) {
+	int res = 1;
+	SCREEN_AT(p->x, p->y) = p->next_char;
+
+	switch (p->dir) {
+		case UP:    p->y--; break;
+		case DOWN:  p->y++; break;
+		case LEFT:  p->x--; break;
+		case RIGHT: p->x++; break;
+	}
+
+	if (SCREEN_AT(p->x, p->y) != EMPTY || p->x < 0 || p->x >= 40 || p->y < 0 || p->y >= 25) {
+		res = 0;
+	}
+	SCREEN_AT(p->x, p->y) = PLAYER;
+
+	return res;
+}
+
+static void play_game(char n_players) {
+	uint16_t busy_wait = 300;
+
+	struct player players[MAX_PLAYERS] = {
+		{  5, 12, RIGHT, 0, 0, CHR_H },
+		{ 35, 12, LEFT,  0, 0, CHR_H },
+	};
+
+	clrscr();
+
+	while(1) {
+		char i;
+		uint16_t n;
+
+		for (i=0; i<n_players; i++) {
+			if (!move_player(&players[i])) {
+				return;
+			}
+		}
+
+		/* "sleep" for a bit, but keep reading joystick changes */
+		for (n=0; n<busy_wait; n++) {
+			for (i=0; i<n_players; i++) {
+				char tmp = joy_read(i);
+				if (tmp) {
+					players[i].joy = tmp;
+				}
+			}
+		}
+
+		for (i=0; i<n_players; i++) {
+			update_player(&players[i]);
+		}
+	}
+}
+
+int main() {
+	joy_install(joy_static_stddrv);
+
+	/* use uppercase character set */
+	*((unsigned char*)0xD018) = 0x14;
+
+	while(1) {
+		play_game(2);
+		printf("game over!");
+	}
+}
-- 
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