How did you implement the theme?
I implemented the concept of the "Road" theme as follows:
The game is a tower defense style game where monsters move from their entrance to the target along a road.
Players can manipulate the road by placing special devices to change the monsters' path.
The more twisted and winding the path becomes, the longer it takes for monsters to travel — but this also reduces the number of available tiles for building tanks and energy machines for defense.

How did you add the special object?
I implemented the special object called Cone as follows:
Each tank requires 4 specific Infinity Cones out of a total of 10 to be built — and so do Machines.
When a tank fires, it consumes 1 corresponding unit of energy, while Machines produce 2 units of energy every 5 seconds for the Cones they are linked to.
If a tank runs out of energy, it can no longer fire.
Players can only extract energy from a maximum of 3 Infinity Cones at a time, so they must carefully decide which Cones to extract, when to extract them, and which tanks are most effective against specific types of enemies — based on the combination of Cones required.