From c3552ae872e3071526263f803cb641d28286f062 Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cobrien@witekio.com>
Date: Tue, 14 Oct 2025 14:34:12 +0100
Subject: [PATCH] Add asteroids

---
 game.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 84 insertions(+), 8 deletions(-)

diff --git a/game.c b/game.c
index 8ee784e..1d66a93 100644
--- a/game.c
+++ b/game.c
@@ -6,11 +6,19 @@
 
 #include <assert.h>
 #include <linux/input-event-codes.h>
+#include <math.h>
 #include <string.h>
 
 #define FIRE_MEAN -0.15
 #define FIRE_JITTER 0.01
 
+#define ASTEROID_MIN_VERTS 5
+#define ASTEROID_VERT_RANGE (MAX_VERTS - ASTEROID_MIN_VERTS)
+#define ASTEROID_A_JITTER 0.8
+#define ASTEROID_VEL_JITTER 0.001
+#define ASTEROID_OMG_JITTER 0.005
+#define INIT_ASTEROIDS 8
+
 #define LIN_PWR 0.0001
 #define ROT_PWR 0.002
 
@@ -22,14 +30,6 @@
 
 #define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
 
-typedef struct {
-	bool visible;
-	int entity;
-	unsigned vert_count;
-	vec2_t verts[MAX_VERTS];
-	uint8_t flags;
-} shape_t;
-
 typedef struct {
 	vec2_t pos;
 	vec2_t vel;
@@ -40,6 +40,20 @@ typedef struct {
 	bool wrap;
 } entity_t;
 
+typedef struct {
+	bool visible;
+	int entity;
+	unsigned vert_count;
+	vec2_t verts[MAX_VERTS];
+	uint8_t flags;
+} shape_t;
+
+typedef enum {
+	ASTEROID_SMALL,
+	ASTEROID_MEDIUM,
+	ASTEROID_LARGE,
+} asteroid_size_t;
+
 static const vec2_t ship_verts[] = {
 	{ 0.0, 0.11 },
 	{ 0.05, -0.07 },
@@ -110,6 +124,65 @@ static void shoot()
 	memcpy(s->verts, shot_verts, sizeof(shot_verts));
 }
 
+static void gen_asteroid_shape(asteroid_size_t size, shape_t *out)
+{
+	float r_mean, r_jitter;
+	switch (size) {
+	case ASTEROID_SMALL:
+		r_mean = 0.05;
+		r_jitter = 0.02;
+		break;
+	case ASTEROID_MEDIUM:
+		r_mean = 0.1;
+		r_jitter = 0.02;
+		break;
+	case ASTEROID_LARGE:
+		r_mean = 0.15;
+		r_jitter = 0.05;
+	}
+
+	const unsigned n
+		= ASTEROID_MIN_VERTS + rng_uint32() % (ASTEROID_VERT_RANGE);
+	out->vert_count = n;
+
+	const float da = 2.0f * PI / n;
+	for (unsigned i = 0; i < n; ++i) {
+		const float r = r_mean + rng_plusminus() * r_jitter;
+		const float a
+		    = i * da + ASTEROID_A_JITTER * rng_plusminus() * da / 2;
+		out->verts[i] = (vec2_t) { r * cosf(a), r * sinf(a) };
+	}
+}
+
+static void add_asteroid()
+{
+	unsigned id;
+	entity_t *e = add_entity(&id);
+	e->wrap = true;
+	e->pos.y = rng_plusminus();
+	e->pos.x = aspect * rng_plusminus();
+	e->vel = (vec2_t) {
+		ASTEROID_VEL_JITTER * rng_plusminus(),
+		ASTEROID_VEL_JITTER * rng_plusminus(),
+	};
+	e->omg = ASTEROID_OMG_JITTER * rng_plusminus();
+
+	shape_t *s = add_shape(id, nullptr);
+	s->visible = true;
+	s->flags = WRAP | CONNECT;
+
+	asteroid_size_t size;
+	const float r = rng_canon();
+	if (r < 0.2)
+		size = ASTEROID_SMALL;
+	else if (r < 0.5)
+		size = ASTEROID_MEDIUM;
+	else
+		size = ASTEROID_LARGE;
+
+	gen_asteroid_shape(size, s);
+}
+
 static void remove_shape(unsigned id)
 {
 	if (id < shape_count - 1) {
@@ -179,6 +252,9 @@ void game_init(float _aspect)
 	fire->flags = WRAP | CONNECT;
 	fire->vert_count = NELEMS(fire_verts);
 	memcpy(fire->verts, fire_verts, sizeof(fire_verts));
+
+	for (unsigned i = 0; i < INIT_ASTEROIDS; ++i)
+		add_asteroid();
 }
 
 void game_update()