private void OnTriggerEnter(Collider other)
        {
            // Collect all the colliders in a sphere from the shell's current position to a radius of the explosion radius.
            Collider[] colliders = Physics.OverlapSphere(transform.position, m_ExplosionRadius, m_TankMask);

            // Go through all the colliders...
            for (int i = 0; i < colliders.Length; i++)
            {
                // ... and find their rigidbody.
                Rigidbody targetRigidbody = colliders[i].GetComponent <Rigidbody>();

                //Don't explode on collision with another projectile
                if (colliders[i].gameObject.CompareTag("projectile"))
                {
                    Debug.Log("Projectile collision");
                    continue;
                }

                // If they don't have a rigidbody, go on to the next collider.
                if (!targetRigidbody)
                {
                    continue;
                }

                // Add an explosion force.
                targetRigidbody.AddExplosionForce(m_ExplosionForce, transform.position, m_ExplosionRadius);

                // Find the TankHealth script associated with the rigidbody.
                SimpleTankHealth targetHealth = targetRigidbody.GetComponent <SimpleTankHealth>();

                // If there is no TankHealth script attached to the gameobject, go on to the next collider.
                if (!targetHealth)
                {
                    continue;
                }

                // Calculate the amount of damage the target should take based on it's distance from the shell.
                float damage = CalculateDamage(targetRigidbody.position);

                // Deal this damage to the tank.
                targetHealth.TakeDamage(damage, m_PlayerNumber);
            }

            // Unparent the particles from the shell.
            m_ExplosionParticles.transform.parent = null;

            // Play the particle system.
            m_ExplosionParticles.Play();

            // Play the explosion sound effect.
            m_ExplosionAudio.Play();

            // Once the particles have finished, destroy the gameobject they are on.
            ParticleSystem.MainModule mainModule = m_ExplosionParticles.main;
            Destroy(m_ExplosionParticles.gameObject, mainModule.duration);

            gm.shellList.Remove(GetComponent <Rigidbody>());

            // Destroy the shell.
            Destroy(gameObject);
        }