When is green 20 safe on Level 202?

After one red/dark opening lane has reduced and there is room for cyan to enter next.

What clears the long submarine roof?

Cyan 20 is the main roof lane; support it with white only when two buffers are available.

Colony Flow! level guide

hard 7 colors

Open the cyan 15/cyan 20/white 20/dark 20 front field, then separate the cyan hull, white belly and green corner traffic.

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Clear the cyan 15/cyan 20/white 20/dark 20 front field without losing the white route.
Use the red 10, dark 15, green 20 and brown 20 second row after the first buffers drain.
Continue cyan and white through the central route, then take the repeated green 20 edge cards.
Finish red, brown and dark outline tails after the centre is open.

Colors in this level:

Cyan, White, Red, Pink, Dark, Green, Brown

Do not bury the white 20 front card under duplicate cyan/green 20 lanes.
Use the green 20 copies after cyan and white open the centre.
Think in chain clears. The best move is the one that sets up the next two moves, not just the quickest current match.

Board notes 5 details

Layout: Cyan-and-white water scene with red, green, brown and dark details. Opening row: cyan 15, cyan 20, white 20, dark 20; below are red 10, dark 15, green 20, brown 20, then white 20, red 20, green 20 and green 20.
Goal: Clear the red ends, cyan hull and roof, white belly, dark windows, and green propeller until the submarine is blank.
Opening: Work the cyan 15/cyan 20/white 20/dark 20 front row before loading the green 20 and red/brown cards underneath.
Danger Zone: Cyan and green both repeat at 20; opening their lower copies before white has a path blocks the central water route.
Mechanics: Cyan-heavy routing board where white cards form the required central break and green cards are later edge traffic.

When is green 20 safe on Level 202?
After one red/dark opening lane has reduced and there is room for cyan to enter next.
What clears the long submarine roof?
Cyan 20 is the main roof lane; support it with white only when two buffers are available.