Add image

Upgrade test target to XCTest.

Rename variables for clarity.

Make debug string easier to parse.

Migrate some code as new instance method.

Replace DPoint ivars in DRange with vector_double2.

Convert Circle.centre to a vector_double2.

Make DPoint a wrapper around simd_double2.

Disable region checking under mouse.

Explicitly reference ivars through self in block.

Remove unused static functions.

Remove explicit declarations of ivars.

Update project settings for Xcode 9.

Fix some warnings caused by macros.

Explanatory comment.