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img element.\n  height: auto;\n}\n\n\n// Retina image\n//\n// Short retina mixin for setting background-image and -size.\n\n@mixin img-retina($file-1x, $file-2x, $width-1x, $height-1x) {\n  background-image: url($file-1x);\n\n  // Autoprefixer takes care of adding -webkit-min-device-pixel-ratio and -o-min-device-pixel-ratio,\n  // but doesn't convert dppx=>dpi.\n  // There's no such thing as unprefixed min-device-pixel-ratio since it's nonstandard.\n  // Compatibility info: https://caniuse.com/css-media-resolution\n...