Great but so simple game, there are so many things to be done.

• User have to reload everytime to load new level.
• Annoying pop up everytime user wins game.
• Static level difficulty, no change in it.
• No tracking of user wins so on basis of that complexity of level could be increased.
• Control movements are so annoying.

• Tracking of user score, adding multiple complexity.
• Before game start user would be able to select complexity then game would decide based on user performance.
• Random colour changing when win instead of dropping them on ground.
• Including timer challenge.

and maybe a thing or more if I got tyme.