Press Any Key to Start

 Step 1
To begin, you can press any Key or click anywhere other than tiles. (Don't click on any of the tiles)

 Step 2
Then any of the four tiles will blink, remember that tile color. Click that same tile.

 Step 2.1
The game would will end if you clicked the wrong tile. You'd have to start the game anew by pressing any key.

 Step 3
If you clicked the correct tile, the level would rise & any tile would blink again: now you must click the previous tile, followed by the current tile, to raise the level.

 Example
Assume red blinks first, then blue blinks second:
The first tile in every sequence would be red; the second tile in each sequence would be blue.
As the level rises, so will the sequence.
The sequence goes on until you click the wrong tile.