cannon.c
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#include "primlib.h"
#include <math.h>
#include <stdlib.h>
struct target {
int x;
int y;
int speed_x;
int is_explosion;
int explosion_counter; // how many times we have already displayed an
// explosion animation
int color;
};
// Draw explosion with the center at coordinates (x,y)
void drawExplosion(int x, int y, float scaling) {
gfx_filledTriangle(x - 7 * scaling, y - 7 * scaling, x + 7 * scaling,
y + 7 * scaling, x + 22 * scaling, y - 22 * scaling, RED);
gfx_filledTriangle(x - 7 * scaling, y - 7 * scaling, x + 7 * scaling,
y + 7 * scaling, x - 22 * scaling, y + 22 * scaling, RED);
gfx_filledTriangle(x - 7 * scaling, y + 7 * scaling, x + 7 * scaling,
y - 7 * scaling, x - 22 * scaling, y - 22 * scaling, RED);
gfx_filledTriangle(x - 7 * scaling, y + 7 * scaling, x + 7 * scaling,
y - 7 * scaling, x + 22 * scaling, y + 22 * scaling, RED);
gfx_filledTriangle(x - 13 * scaling, y, x + 13 * scaling, y, x,
y - 35 * scaling, RED);
gfx_filledTriangle(x - 13 * scaling, y, x + 13 * scaling, y, x,
y + 35 * scaling, RED);
gfx_filledTriangle(x, y - 13 * scaling, x, y + 13 * scaling, x - 35 * scaling,
y, RED);
gfx_filledTriangle(x, y - 13 * scaling, x, y + 13 * scaling, x + 35 * scaling,
y, RED);
}
void draw_target(struct target *t) {
if (!t->is_explosion)
gfx_filledRect(t->x - 10, t->y - 10, t->x + 10, t->y + 10,
t->color); // target
if (t->is_explosion) {
drawExplosion(t->x, t->y + t->explosion_counter * 10,
t->explosion_counter / 5.0);
}
}
void move_target(struct target *t) {
if (!t->is_explosion) {
t->x += t->speed_x;
if (t->x > gfx_screenWidth())
t->x = 0;
if (t->x < 0)
t->x = gfx_screenWidth() - 1;
}
if (t->is_explosion) {
t->explosion_counter += 1;
}
if (t->is_explosion && (t->explosion_counter == 10)) {
t->is_explosion = 0;
t->x = 0;
}
}
// draw isosceles trapezoid with the center of larger base at (x1,y1), center of smaller base at (x2,y2)
// width - width of larger base, taper - ratio of smaller base to larger base
// see drawing in bullet.png
void draw_bullet(int x1, int y1, int x2, int y2, int width, double taper, int color) {
// define vector representing the central line
int dx = x2 - x1;
int dy = y2 - y1;
// define vector perpendicular to the central line
int dx_p = dy;
int dy_p = -dx;
double len = hypot(dx_p, dy_p);
// scale its length to proper width
int dx_p_s = width / (2.0 * len) * dx_p;
int dy_p_s = width / (2.0 * len) * dy_p;
// scale the vector by taper
int dx_p_s_t = dx_p_s * taper;
int dy_p_s_t = dy_p_s * taper;
// compute corners
int x1c = x2 - dx_p_s_t;
int y1c = y2 - dy_p_s_t;
int x2c = x2 + dx_p_s_t;
int y2c = y2 + dy_p_s_t;
int x3c = x1 - dx_p_s;
int y3c = y1 - dy_p_s;
int x4c = x1 + dx_p_s;
int y4c = y1 + dy_p_s;
gfx_filledTriangle(x1c, y1c, x2c, y2c, x3c, y3c, color);
gfx_filledTriangle(x4c, y4c, x2c, y2c, x3c, y3c, color);
}
int main() {
if (gfx_init())
exit(3);
double angle = 90.0 * (M_PI / 180.0);
double bullet_distance;
int is_shooting = 0;
double fire_angle;
const int num_targets = 3;
struct target t[num_targets];
t[0].x = 0;
t[0].y = 40;
t[0].speed_x = 3;
t[0].is_explosion = 0;
t[0].color = MAGENTA;
t[1].x = 1000;
t[1].y = 80;
t[1].speed_x = -5;
t[1].is_explosion = 0;
t[1].color = WHITE;
t[2].x = 100;
t[2].y = 120;
t[2].speed_x = 7;
t[2].is_explosion = 0;
t[2].color = GREEN;
while (1) {
double delta_angle = 2.0 * (M_PI / 180.0);
int x1_barrel = 150 * cos(angle - delta_angle);
int y1_barrel = 150 * sin(angle - delta_angle);
int x2_barrel = 150 * cos(angle + delta_angle);
int y2_barrel = 150 * sin(angle + delta_angle);
gfx_filledRect(0, 0, gfx_screenWidth() - 1, gfx_screenHeight() - 1, BLUE);
gfx_filledCircle(gfx_screenWidth() / 2, gfx_screenHeight(), 100, YELLOW);
gfx_filledTriangle(gfx_screenWidth() / 2, gfx_screenHeight(),
gfx_screenWidth() / 2 + x1_barrel,
gfx_screenHeight() - y1_barrel,
gfx_screenWidth() / 2 + x2_barrel,
gfx_screenHeight() - y2_barrel, YELLOW);
for (int i = 0; i < num_targets; ++i)
draw_target(&(t[i]));
// bullet position wrt the center of the bottom of the screen
int x_bullet_begin = bullet_distance * cos(fire_angle);
int y_bullet_begin = bullet_distance * sin(fire_angle);
int x_bullet_end = (bullet_distance + 30) * cos(fire_angle);
int y_bullet_end = (bullet_distance + 30) * sin(fire_angle);
// bullet position wrt the top-left corner
int x_bullet_begin_tlc = gfx_screenWidth() / 2 + x_bullet_begin;
int y_bullet_begin_tlc = gfx_screenHeight() - y_bullet_begin;
int x_bullet_end_tlc = gfx_screenWidth() / 2 + x_bullet_end;
int y_bullet_end_tlc = gfx_screenHeight() - y_bullet_end;
if (is_shooting) {
draw_bullet(x_bullet_begin_tlc, y_bullet_begin_tlc, x_bullet_end_tlc,
y_bullet_end_tlc, 10, 0.5, RED);
}
gfx_updateScreen();
if (is_shooting) {
for (int i = 0; i < num_targets; ++i) {
if (hypot(x_bullet_begin_tlc - t[i].x, y_bullet_begin_tlc - t[i].y) <
50) {
t[i].is_explosion = 1;
t[i].explosion_counter = 0;
}
}
bullet_distance += 10.0;
}
for (int i = 0; i < num_targets; ++i)
move_target(&(t[i]));
if (gfx_isKeyDown(SDLK_RIGHT))
angle -= 1.0 * (M_PI / 180.0);
if (gfx_isKeyDown(SDLK_LEFT))
angle += 1.0 * (M_PI / 180.0);
if (gfx_isKeyDown(SDLK_SPACE)) {
is_shooting = 1;
bullet_distance = 170.0;
fire_angle = angle;
}
SDL_Delay(10);
};
return 0;
}