It creeps and leaps, it glides and slides.

它會爬行、會跳躍、 會滑動、會滑行。

It’s also unstoppable: weapons, fire, extreme temperatures… no matter what you throw at it, it just regrows and continues its rampage.

而且它還所向無敵： 武器、火、極端溫度... 不論你用什麼方式攻擊它， 它總會再生並繼續製造暴亂。

Its expansion is breathtaking; it doubles in size every hour.

它的擴展能力十分驚人；每小時，它的大小就會變成兩倍。

But there’s one opportunity: after each hour, it goes to sleep, forming itself into a flat triangle and resting for a few minutes before it begins eating and growing again.

但我們有一個機會：每隔一小時它會進入睡眠， 將自己的形狀變成扁平三角形後休息個幾分鐘，接著又會再開始吞噬一切並繼續成長。

Your only chance to save the planet involves a satellite-mounted nano-fission ray that can cut through the blob.

你只有一個機會能拯救地球，而這要用到裝在衛星上的奈米分裂光束來將它切成兩半。

When the blog is active it heals itself within seconds.

當怪物在活動時，只要幾秒鐘的時間它就會癒合。

However, when you break the sleeping blob into two triangles, you make a critical discovery.

然而，當你把在睡眠中的怪物切成兩個三角形後，有了重大的發現。

The acute triangle portion, with all angles less than 90 degrees, is inert.

被切成銳角三角形的部分，也就是所有的角都小於 90 度的三角形，已不再具有生命力。

It never “wakes up.”

它再也不會「醒來」。

The obtuse triangle, which has an angle greater than 90 degrees, wakes up as usual and keeps growing.

至於鈍角三角形，也就是有一個角大於 90 度的三角形，還是一樣會醒來並繼續成長。

Similar experiments show that all shapes other than acute triangles, including right triangles, will also wake up.

類似的實驗結果顯示， 除了銳角三角形之外的所有形狀，包括直角三角形，都還是會醒來。

For the next few minutes, the blob is sleeping in its obtuse triangle form.

接下來的幾分鐘，怪物會以扁平三角形的形式進入睡眠。

You can make clean, straight-line cuts between any two points on or inside the triangle.

你可以針對三角形上或三角形內選定的任兩個點，做到精準的直線切割。

But you’ll only have time to make 7 cuts while the satellite is above you.

但當衛星通過你上方時，可以進行切割的時間只夠你切七次。

By the time it completes its orbit and returns, the blob will have consumed the entire world, if even a single portion that will wake up remains.

當衛星完成繞行再回來時，就已經來不及阻止怪物把整個世界吞噬了，所以你萬萬不可以讓任何一個部分醒過來。

How can you cut the blob entirely into acute triangles and stop it from destroying the planet?

如此一來，你要如何把怪物完全切割成銳角三角形，以阻止它摧毀地球？

Pause the video now to figure out for yourself

[如果你希望自己嘗試解題，請在此暫停。]

Answer in 3, 2 ,1.

[答案即將公布：3、2、1]

While this seems doable at first, there’s a hidden difficulty when it comes to avoiding obtuse and right angles.

雖然一開始這個方法看似可行， 但若想避免鈍角和直角，便會碰到一個隱藏的困難點。

Every time you make a cut that reaches an edge, it either makes an acute and an obtuse angle, or two right angles.

每當切割處接觸到邊緣時，就一定會製造出一個銳角和一個鈍角，不然就是兩個直角。

That makes it seems like you’re doomed to keep creating obtuse angles.

看起來似乎你注定會 一直製造出鈍角。

But as with so many of life’s problems, we can look to pizza for inspiration.

但，就像許多人生難題一樣，我們能從比薩上找到靈感。

Imagine squaring off the outside of a pizza, so that instead of a circle, it’s an octagon.

想像一下，把披薩的外緣切平， 讓它變成八角形，而不是一個圓。

When we cut it into slices, each of the eight triangles is acute.

當我們把它切片後，這八個三角形都是銳角三角形。

This works with larger polygons too.

對於邊數更多的多邊形， 這招也一樣可行。

Importantly, it also works for some polygons with fewer sides, including heptagons, hexagons, and pentagons.

重要的是，對於邊數更少的多邊形仍然可行，包括七角形、六角形、五角形。那是好消息，

That’s good news, because if you cut off the sharp corners of the blob triangle, a pentagon is exactly what you’ll be left with.

這可是好消息，因為如果把怪物三角形的尖角切除後，便會得到一個五角形。

And just like a pizza, you can cut the blob pentagon into 5 acute triangles.

而就像比薩一樣， 你可以把怪物五角形切成五個銳角三角形。

That’s 7 cuts, and it renders the blob completely inert.

在切了七次之後，怪物的生命跡象就完全消失了。

You’ve saved the day!

你拯救了世界！

Now you just need to figure out what to do with all of these giant, practically indestructible triangles.

現在，你只需要想辦法處理這些巨大又無法破壞的三角形就行了。

Here is a bonus riddle for you: are triangles the best shape?

以下是額外附上的謎題：三角形是最棒的形狀嗎？

Just kidding, that's not a riddle — but it is worth discussing! Watch these lessons and decide for yourself.

開玩笑的，這其實不是什麼謎題－但它確實是值得討論的一個問題！觀賞這些課程來找出答案吧。