Ostrava Days 2023 is a festival of contemporary avant-garde and experimental classical music. The overall visual concept is based on the abbreviation OD, on the shape of the letters and their mutual color interaction with the underlying surface in combination with distinctive typography. The main “O” shape can be understood as an energetic point or a musical intervention, the hidden “D” as a complementary harmonic note with a light swing and a sharp contour, and the complementary color area in the background as a contrasting answer. On another level, it is a free fantasy of summer time and an image reminiscent of the summer sky with its passing phenomena and our predictions. (photo: Martin Popelář)