Ready. Set. Go!

Makefile

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+all: wasm/game.wasm
+
+wasm/game.wasm: game.c
+	clang --target=wasm32 -I./include --no-standard-libraries -Wl,--no-entry -Wl,--allow-undefined -Wl,--export=game_init -Wl,--export=game_frame -Wl,--export=game_over -o wasm/game.wasm game.c -DPLATFORM_WEB

game.c

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+#include <raylib.h>
+#include <raymath.h>
+
+#define BALL_RADIUS 100.0
+#define GRAVITY 1000.0
+
+static Vector2 ball_position = {0};
+static Vector2 ball_velocity = {200, 200};
+
+void game_frame()
+{
+    BeginDrawing();
+        ClearBackground((Color){20, 20, 20, 255});
+        float dt = GetFrameTime();
+        ball_velocity.y += GRAVITY*dt;
+        float x = ball_position.x + ball_velocity.x*dt;
+        if (x - BALL_RADIUS < 0.0 || x + BALL_RADIUS >= GetScreenWidth()) {
+            ball_velocity.x *= -1.0f;
+        } else {
+            ball_position.x = x;
+        }
+        float y = ball_position.y + ball_velocity.y*dt;
+        if (y - BALL_RADIUS < 0.0 || y + BALL_RADIUS >= GetScreenHeight()) {
+            ball_velocity.y *= -1.0f;
+        } else {
+            ball_position.y = y;
+        }
+        DrawCircleV(ball_position, BALL_RADIUS, RED);
+    EndDrawing();
+}
+
+void game_init()
+{
+    InitWindow(800, 600, "Hello, from WebAssembly");
+    SetTargetFPS(60);
+
+    int w = GetScreenWidth();
+    int h = GetScreenHeight();
+    ball_position.x = w/2;
+    ball_position.y = h/2;
+}
+
+void game_over()
+{
+    CloseWindow();
+}
+
+#ifndef PLATFORM_WEB
+int main()
+{
+    game_init();
+    while (!WindowShouldClose()) {
+        game_frame();
+    }
+    game_over();
+    return 0;
+}
+#endif

include/math.h

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+// Phony math.h. Since we are compiling with --no-standard-libraries we raymath.h can't find math.h.
+// But it only needs it for few function definitions. So we've put those definitions here.
+#ifndef MATH_H_
+#define MATH_H_
+float floorf(float);
+float fabsf(float);
+double fabs(double);
+float fmaxf(float, float);
+float fminf(float, float);
+float sqrtf(float);
+float atan2f(float, float);
+float cosf(float);
+float sinf(float);
+float acosf(float);
+float asinf(float);
+double tan(double);
+#endif // MATH_H_