Solving problems is my favorate way of practicing , however if i solve 3 problems or 100 problems a day the activity grid will be colored by dark green So I suggest to add a new color to the daily activity grid which doesn't appear if you didn't solve at least 10 or some number of problems . So if you solve 10 problems the grid will be black that's would motivate me and other users and it's easy to add to the website , so why not ?