Line an 8x8 baking dish with parchment paper or lightly oil a square silicone cube mold.

In a saucepan, whisk the agar-agar powder into the cold filtered water. Let sit for 5 minutes to hydrate.

Bring the water and agar to a rolling boil over medium-high heat, whisking constantly. Boil vigorously for 2 to 3 minutes.

Add the granulated sugar and stir until fully dissolved. Return to a boil and simmer for 2 more minutes until the liquid is clear and slightly syrupy.

Remove from heat and quickly divide the hot syrup into 4 separate bowls.

Quickly whisk in 1/4 tsp of a different flavor extract and a drop of coordinating food coloring into each bowl. Add a pinch of citric acid if using.

Pour the colored mixtures into your prepared molds. Let set at room temperature for 2 to 3 hours until completely firm.

Remove from molds, cut into uniform bite-sized cubes with a sharp knife, and wrap individually in clear cellophane candy wrappers.