chore: add comments to swarm.hpp

src/main.cpp

@@ -65,12 +65,21 @@ main(int argc, char **argv) {
 	scr.draw();
     };
 
+    // We draw to the screen at a rate of `kFPS', but step()ing the swarm at
+    // this rate would be far too fast to be interesting to look at. On the
+    // other hand, step()ing once a second is too slow.
+    //
+    // So, we step() every quarter second. To line up the move() so that a unit
+    // move() happens preceding each step(), we also need to move as fast as
+    // we've shortened our step() interval.
     for(int i = 0; i < iter_count * kFPS/4;) {
 	if(!pause) {
 	    scr.clear();
 
 	    update_and_draw();
 
+	    // Since we step() 4x a second, we need to move() 4x as fast as moving by dt
+	    // each frame.
 	    swarm.move(kDT * 4);
 	    if(i % (kFPS/4) == (kFPS/4)-1)
 		swarm.step();
@@ -152,6 +161,7 @@ main(int argc, char **argv) {
 	    break;
 	}
 
+	// Wait for kDT (time between two frames)
 	usleep(1000 * 1000 / kFPS);
     }