U++

I think it would be nice if Ultimate++ will support CSS 3 higlight. When I was writing this improvement I have used following site: http://www.w3schools.com/cssref/

More over I devided my code into sections. Each section corresponds to the section on w3schools website.

        // CSS3
        "opacity", // <- End Section (Color Properties)
        "background-clip", "background-origin", "background-size", "border-bottom-left-radius", "border-bottom-right-radius",
        "border-image", "border-image-outset", "border-image-repeat", "border-image-slice", "border-image-source",
        "border-image-width", "border-radius", "border-top-left-radius", "border-top-right-radius", "box-decoration-break", 
        "box-shadow", // <- End Section(Background and Border Properties)
        "overflow-x", "overflow-y", // <- End Section etc.
        "align-content", "align-items", "align-self", "flex", "flex-basis", "flex-direction", "flex-flow", "flex-grow",
        "flex-shrink", "flex-wrap", "justify-content", "order",
        "hanging-punctuation", "hyphens", "line-break", "overflow-wrap", "tab-size", "text-align-last", "text-justify",
        "word-break", "word-wrap",
        "text-decoration-color", "text-decoration-line", "text-decoration-style", "text-shadow", "text-underline-position",
        "animation", "animation-delay", "animation-direction", "animation-duration", "animation-fill-mode",
        "animation-iteration-count", "animation-name", "animation-timing-function", "animation-play-state",
        "backface-visibility", "perspective", "perspective-origin", "transform", "transform-origin", "transform-style",
        "transition", "transition-property", "transition-duration", "transition-timing-function", "transition-delay",
        "box-sizing", "nav-down", "nav-index", "nav-left", "nav-right", "nav-up", "outline-offset", "resize", "text-overflow",
        "break-after", "break-before", "break-inside", "column-count", "column-fill", "column-gap", "column-rule",
        "column-rule-color", "column-rule-style", "column-rule-width", "column-span", "column-width", "columns",
        "marks",
        "filter",
        "image-orientation", "image-rendering", "image-resolution", "object-fit", "object-position",
        "mask", "mask-type",
        "mark", "mark-after", "mark-before", "phonemes", "rest", "rest-after", "rest-before", "voice-balance",
        "voice-duration", "voice-pitch", "voice-pitch-range", "voice-rate", "voice-stress", "voice-volume",
        "marquee-direction", "marquee-play-count", "marquee-speed", "marquee-style",

Moreover, Personally I think that CSS highlight engine needs some minor changes. I will try to implement it in near feature.