Pyramid Solitaire is an ultra-classic card game. You must eliminate all the cards by removing pairs that add up to 13. You can only use the card that are free, that is to say, cards that are not covered by other cards.
There is nothing in particular to remark about David's Pyramid Solitaire, the game is well made and fun.
A small blemish however is that it requires installation of runtimes that are particularly hefty if you have never needed: Visual Basic, NSBasic or S309PictureBox Control.