Single File
SFC is a single file, easy to copy/paste into Blackboard Ultra.
Free as in Freedom and as in Free Beer
SFC is free and open source.
No Gradebook Integration
SFC is designed to help students practice, not to evaluate their practice. It is a practice / study / engagement tool, not an assessment tool.
Developer Friendly
Cards are defined as an array of constants. Customizing them requires basic code editing skills. The only authoring tool you need is a text editor.