v2.1 - September 2017

Notable User Changes:

• Added the dynamic phase gradient gate "Grad^t"
• Worked around a Chrome bug causing shader compilation to fail
• The NOT gate is now drawn as a circled plus even when uncontrolled or in the toolbox.
• Fixed permutation gates with coherent controls not being disabled when applied to measured qubits.
• Added a "clear circuit" button that doesn't remove custom gates
• Location-independent gates (e.g. set-input gates and global phase gates) are now drawn as octagons
• Set-input gates are now considered "non-local" and show a vertical dashed line
• Removed reversed-input gates from toolbox
• Fixed gates not being removed when middle-clicking through their resize tab
• Change the phase gradient gate's symbol to "Grad^1/2"
• Entering a single value when defining a custom matrix gate now produces a global phase gate
• X/Y post-selection gates symbols now use circled characters
• Fixed a precision-loss bug in the shader used by phase gradient gates

Notable Dev Changes:

• Renamed the template folder to html
• Added hidden modular-multiply-accumulate and pivot-flip gates
• Added license headers (Quirk's copyright is now owned by Google)
• Added utility testing methods for gates that only perform phasing
• Test pages now include a progress indicator
• Worked around travis-ci adding enough webgl support to run circuit tests, but not enough to pass all of them
• ketShaderPhase now works with angles instead of complex unit values.