Burn stuff to prevent yourself from freezing

Bonus info in case the tutorial wasn't enough:

The thermometer shows your temperature: each small tick shows 5C and each big tick shows 20C. Your temperature gradually goes down faster and faster, and if you go below 0C you lose.

You can buy fuel, lighters and upgrades in the shop. 

You can't have more than 4 unlit fuel in your furnace at the same time (you can buy the larger furnace upgrade to increase this number). 

Use lighters to light fuel on fire. 

You can buy upgrades with burnbux. You gain 1 burnbuck for every fuel lit on fire.

You get money from lighting fuel on fire. Fuels have their own mults which get summed up and multiplied by the lighter's money per mult stat when they're set on fire. You gain an additional 10% money bonus for each fuel lit at the same time, so try to light as much fuel as you can with your lighters.

There's not really any goal besides surviving as long as possible, try going for a diamond!