To execute this geometric haven, cut two pairs of angled rafter legs from two-by-two-inch solid oak lumber, mitering the top apex joints at thirty and sixty-degree complementary angles to create an off-center A-frame profile. Join the rafter pairs with a horizontal ridge beam and lower base stretchers using blind dowel joinery and wood glue, clamping the frame until rock-solid. Cut three-quarter-inch oak plywood panels to clad the rear triangle and one side of the slanted roof, leaving the opposite roof face open with three horizontal security slats for light and ventilation. Cut a triangular or arched front entry through the front facade board, smoothing all interior angles with a round-over router bit. Fit the bottom floor with a removable cedar plank deck resting on vibration-damping silicone pads. Sand all timber surfaces to a fine two-hundred-and-twenty-grit finish, apply a coat of natural Danish oil or matte beeswax, and insert a plush faux-fur mat into the triangular den.