Mix crushed pretzels, butter, and 1/2 C sugar. Pat into 9 x13 baking dish. Bake at 350 degrees for 8 minutes. Beat cream cheese, 1 C sugar, and Cool Whip together and spread on top of pretzel crust. Dissolve jello in 2 C boiling water. Add strawberries; chill until slightly set. Pour the jello mixture over the cream cheese mixture. Chill until hard.