Sailtrim Upwind one shows you exactly what happens when you adjust each of the sail trim options. It explains what happens when you adjust each of the various trimming functions on your sailboat to make your boat go faster.
You can select the sail you want to trim (mainsail or headsail). Then you can experiment with a choice of different trimming functions, operated by sliders, to either trim or ease the sheet virtually. You can immediately see the change in sail shape and get information on the wind and wave conditions for which this trim might be good.