feat: velocity tracking w/ rendering lines

src/Game.cpp

@@ -1,8 +1,8 @@
 #include "Game.hpp"
 
 #include <SFML/Window/Event.hpp>
+#include <cmath>
 
-#include "Ball.hpp"
 #include "Constants.hpp"
 #include "VectorMath.hpp"
 
@@ -61,9 +61,47 @@ void Game::update() {
     for (auto& object : m_objects) object->update(dt);
 }
 
+void Game::drawLine(const sf::Vector2f& start, const sf::Vector2f& direction,
+                    float length, const sf::Color& color) {
+    float dirLength =
+        std::sqrt(direction.x * direction.x + direction.y * direction.y);
+    sf::Vector2f dirNorm =
+        (dirLength != 0.f) ? direction / dirLength : sf::Vector2f(1.f, 0.f);
+    sf::Vector2f endPoint = start + dirNorm * length;
+
+    sf::Vertex line[] = {{start, color}, {endPoint, color}};
+    m_window.draw(line, 2, sf::PrimitiveType::Lines);
+}
+
+void Game::drawDirectionLine(const Ball* ball) {
+    sf::Vector2f ballCenter = ball->getPosition();
+    sf::Vector2i mousePixel = sf::Mouse::getPosition(m_window);
+    sf::Vector2f mouseWorld(static_cast<float>(mousePixel.x),
+                            static_cast<float>(mousePixel.y));
+    sf::Vector2f dir = mouseWorld - ballCenter;
+    drawLine(ballCenter, dir, 100.f, sf::Color::Green);
+}
+
+void Game::drawVelocityLine(const Ball* ball) {
+    if (ball->isAtRest()) return;
+    sf::Vector2f ballCenter = ball->getPosition();
+    sf::Vector2f velocity = ball->getVelocity();
+    float velLength =
+        std::sqrt(velocity.x * velocity.x + velocity.y * velocity.y);
+    float clampedLength = std::min(100.f, std::max(0.f, velLength));
+    drawLine(ballCenter, velocity, clampedLength, sf::Color::Blue);
+}
+
 void Game::render() {
     m_window.clear(sf::Color::Black);
     for (auto& object : m_objects) object->draw(m_window);
+
+    auto* ball = dynamic_cast<Ball*>(m_objects[0].get());
+    if (ball) {
+        drawDirectionLine(ball);
+        drawVelocityLine(ball);
+    }
+
     m_window.display();
 }