Examples

Sand

🟨 -> ⬛
⬛ -> 🟨

🟨   -> ⬛   ↔
  ⬛ ->   🟨

1D World

🌱 = >0 >0 >0
🌿 = 🔴-1 🟢-1 🔵-1
💥 = 🌿🌿

🌱 -> 💥

Direction Water

💧 = ⬜🟦
💦 = 🟦⬜

💧 -> ⬛
⬛ -> 💧

💧⬛ -> ⬛💧 ↔
     ⬇
💧⭐ -> 💦⭐

Bouncing Rocket

👉 = 🟧⬜

👆 = ⬜
     🟧

👉⬛ -> ⬛👉 ↻
     ⬇
👉⭐ -> 👆⭐

Powder

First define powder:

⛰ = ⭐
     ⬛
     
⛰ -> ⬛
⬛ -> ⛰

⛰   -> ⬛   ↔
  ⬛ ->   ⛰

Now we can make whatever powder elements we want:

⏳ = 🟨
     ⬛
          
❄ = ⬜
     ⬛

Timer

This red timer counts down from 10, and then turns blue.

⏰ = ⬜
     🟥

🏁 = ⬛
     🟥
               
⚡ = 🔴-1 🟢-1 🔵-1

⭐ -> ⚡
🟥 -> 🟥

🏁 -> 🟦

Explosion

💣 = 🟧
     ⬜

🏁 = 🟧
     ⬛

⚡ = 🔴-1 🟢-1 🔵-1

💥 = 🟧 -> 🟧
     ⭐    ⚡

💥⬛ -> 💥💥 ↻

🏁 -> ⬛