INCREASING AND DOUBLE COMPARATIVE

Comparison and contrast are expressed by the use of the…the… with comparative adjectives in parallel clauses. This structure is used to show proportionate increase or decrease.
The more adventurous it is, the more I like it. (NOT The more it is adventurous, the more I like it.)

A short form of this structure is used in the expressions

‘the more the merrier’

‘How do you like your coffee?’ ‘The stronger the better.’

We also use expressions like easier and easier and more and more to show gradual increase. It's important to say that something is increasing all the time. 

He was driving faster and faster.
It kept raining harder and harder
As he was explaining it I got angrier and angrier

If you want to practice with online activities:
Double comparatives: ESLlounge or Oxford University
Increasing comparatives: TolearnEnglish or agendaweb

TO download the PPT about comparatives and superlatives: Power Point