diff --git a/src/drone_controller.cc b/src/drone_controller.cc
index 514a166..3284acf 100644
--- a/src/drone_controller.cc
+++ b/src/drone_controller.cc
@@ -116,7 +116,7 @@ void DroneController::seek(int frame) {
 
 
 void DroneController::computeCollisions(double sphere_radius) {
-	double sqDist = sphere_radius * sphere_radius * 2;
+	double sqDist = sphere_radius * sphere_radius * 4;
 	for (int i = 0; i < duration; i++) {
 		for (Drone &a : drones) {
 			a.setTo(i);
diff --git a/src/main_window.cc b/src/main_window.cc
index 9680d94..1e9f054 100644
--- a/src/main_window.cc
+++ b/src/main_window.cc
@@ -92,8 +92,6 @@ void MainWindow::open(const QString &path) {
 	settings_pane->setEnabled(true);
 
 	glw.setPainter(dc);
-
-	dc->computeCollisions(.1);
 	pause();
 }
 
diff --git a/src/settings_pane.cc b/src/settings_pane.cc
index fe2abd3..096bc08 100644
--- a/src/settings_pane.cc
+++ b/src/settings_pane.cc
@@ -10,6 +10,7 @@
 SettingsPane::SettingsPane(QWidget *parent)
 	:QWidget(parent) {
 	QDoubleSpinBox *sphere_radius = new QDoubleSpinBox();
+	sphere_radius->setSingleStep(.1);
 	QCheckBox *show_trajectories = new QCheckBox();
 	QCheckBox *show_support_lines = new QCheckBox();
 	collisions = new QListWidget();