When you tunnel the fegundo across the room, you should remove as much briar as possible on your way.

×In a situation like this, if the fegundo keeps moving east, it removes 3 squares of briar for every square it progresses. (

f = fegundo just before exploding)

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bbbbbb bbbbb bbbb bbb
fbbbbbb fbbbbb fbbbb fbbb
bbbbbb bbbbb bbbb bbb
bbbbbbbbb bbbbbbbbb bbbbbbbbb bbbbbbbbb
bbbbbbbbb bbbbbbbbb bbbbbbbbb bbbbbbbbb

If, instead the fegundo moves northeast, then southeast, then northeast, then southeast, the fegundo removes 4-5 squares of briar for every square it progresses. This gives the briar more room to grow in, thus giving you more time to complete the room.

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bbbbbb bbbbbb bbbb bbbb
bbbbbb fbbbbb bbbb fbbb
fbbbbbb bbbbb fbbbb bbb
bbbbbbbbb b bbbbb b bbbbb b bbb
bbbbbbbbb bbbbbbbbb bbbbbbbbb bbbbbbbbb