Wind Zones For Doobers
A common practice in mobile games is to have currencies or collectible images pop out of somewhere and get sucked into another place. Rather than handling this entirely through code, I prefer using Unity Wind Zones.
After making a Wind Zone, it is placed on the container/meter/target for where the particles should fly. Setting the Mode to "Spherical" and Main value to a negative number will cause the particles to get sucked toward the epicenter of the Wind Zone.
On the same Wind Zone game object, I will add a collider and scale it so that it is roughly the same size of whatever container it is affecting. This will be for destroying the particles once they have reached their destination. For UI elements, it helps if the collider is extended along the z-axis.
Otherwise, they will have a tendency to fly right through the target and continue to orbit the Wind Zone. Like so:
Depending on the desired effect, a collider may not be necessary. Sometimes it just needs a little love <3
A layer named "WindZone" is created and the game object with the Wind Zone is set to that layer. In the particle system, "External Forces" and "Collision" are enabled. The "Influence Mask" and "Collides With" settings are set to the "WindZone" layer so that the particles will not be affected by any other colliders, including those on buttons in the UI.
To make the particles behave more naturally, I will also animate the Main and Radius values on the Wind Zone in such a manner so they gradually increase over time and have more of a vacuuming effect. Increasing the Radius will cause those particles closest to the Wind Zone epicenter to get sucked in first and by making it scale up to the size of the entire screen, it will guarantee there will be no straggler particles on the outer edges.