Continuous effects sandbox. Create Magic: the Gathering cards, add abilities to them, and then see how they interact with each other on the battlefield. This is an interactive sandbox for the Comprehensive Rulebook rule 613 (Interaction of Continuous Effects).
You can only add static abilities that change the characteristics of permanents, and a couple of "primitive" abilities.
A primitive ability is only a single line: "flying", "first strike" or "haste".
Other abilities consist of one or more lines that define the "subjects" and one or more lines that define the "changes" to those subject's characteristics.
Defining subjects. A subject may be this (meaning 'this permanent') or a set of permanents that satisfy all requirements on a line. These requirements may be a type (such as 'creature'), a subtype (such as 'Bear'), a color (such as 'red'), a lack of these characteristics (such as 'nonblack' or 'noncreature') or the word 'youcontrol' or 'nocontrol'.
Defining changes. A line such as "1/2" means adding "+1/+2" to the subjects; otherwise changes may be the following directives:
switch switches power and toughness
silence: lose all abilities
losecolors: lose all colors
setcolor:[colorname]: becomes [colorname]
addcolor:[colorname]: is [colorname] in addition to other colors
addtype:[cardtype]:is [cardtype] in addition to other types