On ISGG's 30th Agenda: Legacy and Challenges -- On the Diagonals of Billiards -- Exploring the Steiner-Soddy Porism -- Circumparabolas in Chapple's porism -- Permutation Cubics -- Beyond the Nine-Point Conic -- Complex Solution of Engineering Problems by Graphic Methods -- Integer Sequences from Circle Divisions by Rational Billiard Trajectories -- Topographic Surfaces as Topological Sets -- Generalizing Continuous Flexible Kokotsakis Belts of the Isogonal Type -- The Intersection Curve of an Ellipsoid with a Torus Sharing the same Center -- Four-Dimensional Visual Exploration of the Complex Number Plane -- Regularity Conditions for Voronoi Diagrams in Hyperbolic Space -- Poncelet and the (Arquimedean) twins -- A Note on Local Intersection Multiplicity of Two Plane Curves -- Locally Flat and Rigidly Foldable Discretizations of Conic Crease Patterns with Reflecting Rule Lines -- Transformations between Developments and Perspectives of Three and Four Dimensional Cubes -- Perfect circles, Amicable Triangles and some of their Properties - Angles Equality and About Two New Constants in the Triangle -- Geometrical Construction of Shape by a Weak-Visual Person in a Physical Medium -- Algebraic Surfaces and their Geometric Bases -- The Wrought Iron Beauty of Poncelet Loci -- Rectification of an Edgy Photograph -- Point Cloud Upsampling via Quadric Fitting -- Viewing Matters -- Geometric Aspects of Modeling Real Conditions of Solar Irradiation of Energy Efficient Architectural Objects -- MPS Simulation for the Japanese Sport Wellness Blowgun -- Conservative Dynamical Systems in Oscillating Origami Tessellations.