Get the source while it's hot! (Mac/Win/Linux/iPhone/etc) Mostly a bug fixing update, but a big one. There are also a number of minor API additions and documentation fixes. Google Code Project Page Cheesy promo video: Youtube Documentation: C API docs/Objective-C API Docs See some games made with Chipmunk on the wiki. Demo app binaries: (Mac, Win, iPhone) CHANGES SINCE 5.3.1: FIX: Collision begin callbacks were being called continuously for sensors or collisions rejected from the pre-solve callback. FIX: Plugged a nasty memory leak when adding post-step callbacks. FIX: Shapes were being added to the spatial hash using an uninitialized bounding box in some cases. FIX: Perfectly aligned circle shapes now push each other apart. FIX: cpBody setter functions now call cpBodyActivate(). FIX: Collision handler targets are released in Objective-Chipmunk when they are no longer needed instead of waiting for the space to be deallocated. API: cpSpaceSegmentQuery() no longer returns a boolean. Use cpSpaceSegmentQueryFirst() instead as it's more efficient. NEW: cpSpaceRehashShape() Rehash an individual shape, active or static. NEW: cpBodySleep() Force a body to fall asleep immediately. NEW: cpConstraintGetImpulse() Return the most recent impulse applied by a constraint. NEW: Added setter functions for the groove joint endpoints. MISC: A number of other minor optimizations and fixes.