add bouncing ball example

examples/shapes/bouncing_ball.zig

@@ -0,0 +1,69 @@
+const rl = @import("raylib");
+
+pub fn main() anyerror!void {
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const screenWidth = 800;
+    const screenHeight = 450;
+
+    rl.initWindow(screenWidth, screenHeight, "raylib-zig [shapes] example - bouncing ball");
+    defer rl.closeWindow(); // Close window and OpenGL context
+
+    var ballPosition: rl.Vector2 = rl.Vector2{
+        .x = @floatFromInt(@divExact(rl.getScreenWidth(), 2)),
+        .y = @floatFromInt(@divExact(rl.getScreenHeight(), 2)),
+    };
+    var ballSpeed: rl.Vector2 = rl.Vector2{ .x = 5.0, .y = 4.0 };
+    const ballRadius: i32 = 20;
+
+    var pause: bool = false;
+    var framesCounter: i32 = 0;
+
+    rl.setTargetFPS(60); // Set our game to run at 60 frames-per-second
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!rl.windowShouldClose()) { // Detect window close button or ESC key
+        // Update
+        //----------------------------------------------------------------------------------
+        if (rl.isKeyPressed(.space)) {
+            pause = !pause;
+        }
+
+        if (!pause) {
+            ballPosition.x += ballSpeed.x;
+            ballPosition.y += ballSpeed.y;
+
+            const ballWidthEdge: f32 = @floatFromInt(rl.getScreenWidth() - ballRadius);
+            if ((ballPosition.x >= ballWidthEdge) or (ballPosition.x <= ballRadius)) {
+                ballSpeed.x = ballSpeed.x * -1.0;
+            }
+
+            const ballHeightEdge: f32 = @floatFromInt(rl.getScreenHeight() - ballRadius);
+            if ((ballPosition.y >= ballHeightEdge) or (ballPosition.y <= ballRadius)) {
+                ballSpeed.y = ballSpeed.y * -1.0;
+            }
+        } else {
+            framesCounter += 1;
+        }
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        rl.beginDrawing();
+        defer rl.endDrawing();
+
+        rl.clearBackground(rl.Color.ray_white);
+
+        rl.drawCircleV(ballPosition, ballRadius, rl.Color.maroon);
+        rl.drawText("PRESS SPACE to PAUSE BALL MOVEMENT", 10, rl.getScreenHeight() - 25, 20, rl.Color.light_gray);
+
+        // On pause, we draw a blinking message
+        if (pause and @mod(@divFloor(framesCounter, 30), 2) == 0) {
+            rl.drawText("PAUSED", 350, 200, 30, rl.Color.gray);
+        }
+
+        rl.drawFPS(10, 10);
+        //----------------------------------------------------------------------------------
+    }
+}