The cycle is two isothermal changes and two adiabatic ones. Heat enters along the hot isotherm, leaves along the cold one, and the two adiabatic legs carry the gas between the two temperatures without any heat crossing.
The efficiency is 1 − Tc / Th, which depends on the two temperatures and on nothing else. No engine working between the same two reservoirs can beat it.
The flow diagram counts Qh as 100. Whatever does not leave as work leaves as Qc into the cold reservoir, so widening the temperature gap thickens the work arrow and thins the one on the right.
The panel names at the top right open and close each panel. Drag a panel by its header to move it: panels snap to each other and to the screen edge, and a panel resting on an edge drops the rounded corner on that side. Double-click a panel title to switch between floating panels and a single fixed panel at the top right. Pick a row in the condition panel and its value appears in the child panel beside it, which follows the parent as it moves.