Hello BurnSim users, a new version has been released and is ready for download at https://burnsim.com/download. New additions include custom 2D grain profiles drawn in program or imported from DXF or SVG and a new axial cross sectional view of the simulated motor. These are brand new features and I've tested quite a bit on my own, but assume there are still lots of bugs lurking in there. Please let me know anything you see that needs addressing. Version 4.0.0.12 - released 8/5/2026 * Added a Custom grain type: draw or import your own grain cross-section instead of picking a parametric shape. Import from an ASCII DXF, SVG, or raster image (PNG/JPEG/BMP), or build one from scratch in the new shape editor - an outer boundary plus repeatable holes and slots you can drag directly in the preview - and export back to DXF when you're done. This feature is brand new - see the caveats on the Download page * Added an axial (side-on) motor cross-section next to the radial preview, showing the grain stack, case, and nozzle for any grain type, with the same erosion slider animating both. Case/nozzle dimensions beyond throat and exit are estimated rather than modeled * Fixed a rasterization bug inflating a D grain's reported peak Kn by roughly 11% - other grain types were unaffected * Removed the Pie Segment grain type (it's no longer offered when adding a grain); a motor file that already has one still opens and explains what happened, instead of failing with an unrecognized-type error * Grain geometry the simulator can't actually represent (e.g. an oversized finocyl fin) is now flagged directly in the grid instead of silently simulating something else * Grains left with no burning surface (e.g. an end burner with both ends inhibited) are now reported instead of crashing the simulation * Sped up simulations where several grains share the same shape by eroding each distinct shape once instead of once per grain * Fixed New, Open, and Recent Files immediately discarding an unsaved motor instead of asking whether to save it first, the way closing the program already did * Fixed an imported custom grain shape occasionally being silently discarded instead of applied to the grain * Fixed the grain editor's toolbar overlapping the grain grid when the window was narrow Thanks! Greg Deputy