MBL 2020 took place on 07-19.09.2020 in Milówka, Poland. Because of the COVID-19 pandemic the camp was organized differently then before. In fact, two camps took place simultaneously. 35 participants from 7 countries and 13 tutors met in Milówka while those who couldn’t travel to Poland took part in a virtual event. In total, there were 67 participants from 19 countries: Poland, Czech Republic, Slovakia, Hungary, Germany, England, Slovenia, Switzerland, Belarus, Croatia, Sweden, Serbia, Georgia, Norway, France, Finland, India, Ukraine and Latvia. Both camps were filled with academic events. Onsite and virtual campers attended the same mathematical classes. There were three blocks of classes, each three days long. On every day there were three 80-minutes long lecture slots, during which participants could choose between their favourite fields of maths, both academic and more olympic-style. After classes campers had the opportunity to discuss the lectures and clear their doubts at TAU (short for time, academic, unscheduled). Finally, there were also Camper Talks during which participants could present their favourite subjects in a form of a short lecture. MBL wouldn’t have been complete without other, non-academic events. After the first block of classes onsite campers went hiking in Beskidy mountains. Meanwhile people from the virtual camp could participate in a team scavenger hunt. The other free day was designated for a team problem solving competition and a fun match (a mathematical quiz with non-standard questions). The rest of the camp was filled with various evening activities (organized by participants as well as the MBL team), sport activities and special events, including relays (another team contest similar to the Náboj competition), questions evening café (where tutors and organizers shared their experience, regarding mostly university life, with participants), or a campfire.