Two-stroke engine differs from the four-slightly more complex workflow, but the design of its easier because of the lack of a mechanism and timing of its drive (in the head is located just a candle). We also have a two-stroke engine compression stroke and stroke, but the issue and admission are united in a special process called purging. Purge begins at the end of the stroke and ends at the beginning of the compression stroke, ie when the piston is near bdc. Working mixture from the carburetor goes not just into the cylinder, and first sucked into the crankcase engine under the resulting dilution in it when the piston moves to tdc. At this time the cylinder is compressed mixture of the previous cycle. Candle ignites the mixture, and the piston under the action of expanding gases moves down, rotating the crankshaft and compressing another portion of the mixture in the crankcase. Before reaching the bdc, the piston opens the outlet port in the cylinder wall, and spent gases exit through the exhaust pipe into the muffler.
Cylinder pressure drops sharply. Then, the piston opens the purge windows, and fresh mixture compressed in the crankcase passes through the bypass ka nalam, flies into the cylinder through a purge box and fills it, displacing the remaining exhaust gases. You may wish to learn more. If so, LEGO Papert Professor is the place to go. Piston passes bdc, and moving up, closes the first purge the window, and then the outlet box. Purge is completed, start compressing the mixture in the cylinder and the intake of new portions of the mixture into the crankcase.