Primary School No. 8 has always been a bit strange, but since the robotics lab was set up in the basement, things have become even more interesting. Tosia and Igor, best friends from sixth grade, loved spending time there after school, constructing robots and dreaming up how they would one day fly into space. One afternoon, while Tosia was programming a new satellite reading machine, Igor noticed something disturbing on the computer screen. A strange green symbol, similar to the letter 'Z' surrounded by three dots, was blinking on it. - Tosiu, look! What is that? - asked Igor, showing the screen. Tosia furrowed her eyebrows. - I've never seen anything like it. Let's check the origin of the signal! After a few minutes of analysis, it became clear that the mysterious signal was coming from very far away. So far away that even a physics teacher wouldn't believe it: from a planet in the Coral galaxy, which they had once read about in an encyclopaedia. The signal repeated itself every eight minutes, as if someone wanted to pay attention. Together they built a miniature probe, which they sent out through the school transmitter. It soon became apparent that the signal was the answer - someone or something had sent them their coordinates and a three-dimensional map of the alien planet, covered with evergreen forests and glittering lakes. Under cover of darkness, Tosia and Igor returned to the laboratory. They were surprised to find the lab already open, although no one was at the entrance. A strange, flickering light was hovering over their position. When they got closer, they saw that in the middle of the table lay a a glowing green crystal. Next to it pulsed a tiny hologram depicting a mysterious figure and the inscription: "Visit us before we go out. This is our last chance." Tosia looked at Igor - you could see excitement and a hint of fear in her eyes. Would they dare to move to an alien world? Will they decipher who the inhabitants of the Green Planet are and why they need help? At the same moment, the crystal flashed even brighter and the door to the workshop slammed shut with a bang....