private void aggregateForces() {
// tell all of the springs to apply their forces
for (Spring s : springs) {
s.applyForce();
}
// tell all the dampers to apply their forces
for (Damper d : dampers) {
d.applyForce();
}
// tell all the zaps to apply their forces
for (Zap z : zaps) {
z.applyForce();
}
}
void add_spring(int start, int end) {
Spring s = new Spring();
s.start = start;
s.end = end;
springs.add(s);
}