diff --git a/core/package.json b/core/package.json
index c8818d3e43..13930ed0c3 100644
--- a/core/package.json
+++ b/core/package.json
@@ -8,6 +8,10 @@
     "node": ">= 8.11"
   },
   "scripts": {
+    "build": "yarn build:css & yarn build:js",
+    "watch": "yarn watch:css & yarn watch:js",
+    "build:css": "cross-env BABEL_ENV=legacy node ./scripts/css/postcss-build.js",
+    "watch:css": "cross-env BABEL_ENV=legacy node ./scripts/css/postcss-watch.js",
     "build:js": "cross-env BABEL_ENV=legacy node ./scripts/js/babel-es6-build.js",
     "build:js-dev": "cross-env NODE_ENV=development BABEL_ENV=legacy node ./scripts/js/babel-es6-build.js",
     "watch:js": "cross-env BABEL_ENV=legacy node ./scripts/js/babel-es6-watch.js",
@@ -21,6 +25,7 @@
     "prettier": "prettier --write \"./**/*.es6.js\" \"./tests/Drupal/Nightwatch/**/*.js\""
   },
   "devDependencies": {
+    "autoprefixer": "^9.6.1",
     "babel-core": "^6.26.0",
     "babel-plugin-add-header-comment": "^1.0.3",
     "babel-preset-env": "^1.4.0",
@@ -40,6 +45,11 @@
     "minimist": "^1.2.0",
     "mkdirp": "^0.5.1",
     "nightwatch": "^1.2.1",
+    "postcss": "^7.0.18",
+    "postcss-calc": "^7.0.1",
+    "postcss-custom-properties": "^9.0.2",
+    "postcss-header": "^1.0.0",
+    "postcss-import": "^12.0.1",
     "prettier": "^1.14.0",
     "stylelint": "^9.10.1",
     "stylelint-checkstyle-formatter": "^0.1.1",
@@ -68,21 +78,19 @@
           [
             "env",
             {
-              "modules": false,
-              "targets": {
-                "browsers": [
-                  "ie >= 9",
-                  "edge >= 13",
-                  "firefox >= 5",
-                  "opera >= 12",
-                  "safari >= 5",
-                  "chrome >= 56"
-                ]
-              }
+              "modules": false
             }
           ]
         ]
       }
     }
-  }
+  },
+  "browserslist": [
+    "ie >= 9",
+    "edge >= 13",
+    "firefox >= 5",
+    "opera >= 12",
+    "safari >= 5",
+    "chrome >= 56"
+  ]
 }
diff --git a/core/postcss.config.js b/core/postcss.config.js
new file mode 100644
index 0000000000..e58d28ee4f
--- /dev/null
+++ b/core/postcss.config.js
@@ -0,0 +1,20 @@
+module.exports = ctx => ({
+  map: !ctx.env || ctx.env !== 'production' ? { inline: false } : false,
+  plugins: [
+    require('postcss-custom-properties')({
+      preserve: false,
+      // Breaks style lint and unnecessary if preserve set to false.
+      // exportTo: 'dist-css/variables.css',
+      importFrom: [
+        './themes/claro/css/src/base/variables.css'
+      ]
+    }),
+    require("postcss-calc"),
+    require('autoprefixer')({
+      cascade: false
+    }),
+    require('postcss-header')({
+      header: `DO NOT EDIT THIS FILE.\nSee the following change record for more information,\nhttps://www.drupal.org/node/2815083\n@preserve`,
+    }),
+  ]
+});
diff --git a/core/scripts/css/changeOrAdded.js b/core/scripts/css/changeOrAdded.js
new file mode 100644
index 0000000000..53c586e2e6
--- /dev/null
+++ b/core/scripts/css/changeOrAdded.js
@@ -0,0 +1,15 @@
+const fs = require('fs');
+const log = require('./log');
+const compile = require('./compile');
+
+module.exports = (filePath) => {
+  log(`'${filePath}' is being processed.`);
+  // Transform the file.
+  compile(filePath, function write(code) {
+    const fileName = filePath.slice(0, -9);
+    // Write the result to the filesystem.
+    fs.writeFile(`${fileName}.css`, code, () => {
+      log(`'${filePath}' is finished.`);
+    });
+  });
+};
diff --git a/core/scripts/css/check.js b/core/scripts/css/check.js
new file mode 100644
index 0000000000..8eefa7e4f8
--- /dev/null
+++ b/core/scripts/css/check.js
@@ -0,0 +1,23 @@
+const chalk = require('chalk');
+const fs = require('fs');
+const log = require('./log');
+const compile = require('./compile');
+
+module.exports = (filePath) => {
+  log(`'${filePath}' is being checked.`);
+  // Transform the file.
+  compile(filePath, function check(code) {
+    const fileName = filePath.slice(0, -9);
+    fs.readFile(`${fileName}.css`, function read(err, data) {
+      if (err) {
+        log(chalk.red(err));
+        process.exitCode = 1;
+        return;
+      }
+      if (code !== data.toString()) {
+        log(chalk.red(`'${filePath}' is not updated.`));
+        process.exitCode = 1;
+      }
+    });
+  });
+};
diff --git a/core/scripts/css/compile.js b/core/scripts/css/compile.js
new file mode 100644
index 0000000000..0fe45e8bb7
--- /dev/null
+++ b/core/scripts/css/compile.js
@@ -0,0 +1,40 @@
+const chalk = require('chalk');
+const log = require('./log');
+const fs = require('fs');
+const postcss = require('postcss');
+const postcssCustomProperties = require('postcss-custom-properties');
+const postcssCalc = require("postcss-calc");
+const postcssImport = require('postcss-import');
+const autoprefixer = require('autoprefixer');
+const postcssHeader = require('postcss-header');
+
+module.exports = (filePath, callback) => {
+  // Transform the file.
+  fs.readFile(filePath, (err, css) => {
+    postcss([
+      postcssImport(),
+      postcssCustomProperties({
+        // Remove converted properties from the generated code. This needs to be
+        // set to ensure that CSS minifiers don't remove the generated values.
+        preserve: false,
+      }),
+      postcssCalc,
+      autoprefixer({
+        // Output without visual cascade for more consistency with existing
+        // Drupal CSS.
+        cascade: false
+      }),
+      postcssHeader({
+        header: `/*\n * DO NOT EDIT THIS FILE.\n * See the following change record for more information,\n * https://www.drupal.org/node/2815083\n * @preserve\n */\n`,
+      }),
+    ])
+    .process(css, { from: filePath })
+    .then(result => {
+      callback(result.css);
+    })
+    .catch(error => {
+      log(chalk.red(error));
+      process.exitCode = 1;
+    });
+  });
+};
diff --git a/core/scripts/css/log.js b/core/scripts/css/log.js
new file mode 100644
index 0000000000..d9637317ff
--- /dev/null
+++ b/core/scripts/css/log.js
@@ -0,0 +1,4 @@
+module.exports = (message) => {
+  // Logging human-readable timestamp.
+  console.log(`[${new Date().toTimeString().slice(0, 8)}] ${message}`);
+};
diff --git a/core/scripts/css/postcss-build.js b/core/scripts/css/postcss-build.js
new file mode 100644
index 0000000000..e7420187b4
--- /dev/null
+++ b/core/scripts/css/postcss-build.js
@@ -0,0 +1,49 @@
+/**
+ * @file
+ *
+ * Provides the build:css command to compile *.pcss.css files to CSS.
+ *
+ * Run build:css with --file to only parse a specific file. Using the --check
+ * flag build:css can be run to check if files are compiled correctly.
+ * @example <caption>Only process misc/drupal.es6.js and misc/drupal.init.es6.js</caption
+ * yarn run build:css -- --file misc/drupal.pcss.css --file misc/drupal.init.pcss.css
+ * @example <caption>Check if all files have been compiled correctly</caption
+ * yarn run build:css -- --check
+ *
+ * @internal This file is part of the core CSS build process and is only
+ * designed to be used in that context.
+ */
+
+'use strict';
+
+const glob = require('glob');
+const argv = require('minimist')(process.argv.slice(2));
+const changeOrAdded = require('./changeOrAdded');
+const check = require('./check');
+const log = require('./log');
+
+// Match only on .pcss.css files.
+const fileMatch = './**/*.pcss.css';
+// Ignore everything in node_modules
+const globOptions = {
+  ignore: './node_modules/**'
+};
+const processFiles = (error, filePaths) => {
+  if (error) {
+    process.exitCode = 1;
+  }
+  // Process all the found files.
+  let callback = changeOrAdded;
+  if (argv.check) {
+    callback = check;
+  }
+  filePaths.forEach(callback);
+};
+
+if (argv.file) {
+  processFiles(null, [].concat(argv.file));
+}
+else {
+  glob(fileMatch, globOptions, processFiles);
+}
+process.exitCode = 0;
diff --git a/core/scripts/css/postcss-watch.js b/core/scripts/css/postcss-watch.js
new file mode 100644
index 0000000000..d241c5b798
--- /dev/null
+++ b/core/scripts/css/postcss-watch.js
@@ -0,0 +1,43 @@
+/**
+ * @file
+ *
+ * Watch changes to *.pcss.css files and compile them to CSS during development.
+ *
+ * @internal This file is part of the core CSS build process and is only
+ * designed to be used in that context.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+const chokidar = require('chokidar');
+
+const changeOrAdded = require('./changeOrAdded');
+const log = require('./log');
+
+// Match only on .pcss.css files.
+const fileMatch = './**/*.pcss.css';
+// Ignore everything in node_modules
+const watcher = chokidar.watch(fileMatch, {
+  ignoreInitial: true,
+  ignored: './node_modules/**'
+});
+
+const unlinkHandler = (err) => {
+  if (err) {
+    log(err);
+  }
+};
+
+// Watch for filesystem changes.
+watcher
+  .on('add', changeOrAdded)
+  .on('change', changeOrAdded)
+  .on('unlink', (filePath) => {
+    const fileName = filePath.slice(0, -9);
+    fs.stat(`${fileName}.css`, () => {
+      fs.unlink(`${fileName}.css`, unlinkHandler);
+    });
+  })
+  .on('ready', () => log(`Watching '${fileMatch}' for changes.`));
diff --git a/core/themes/seven/css/base/elements.css b/core/themes/seven/css/base/elements.css
index 7fa40e5558..f2aec247dc 100644
--- a/core/themes/seven/css/base/elements.css
+++ b/core/themes/seven/css/base/elements.css
@@ -1,3 +1,9 @@
+/*
+ * DO NOT EDIT THIS FILE.
+ * See the following change record for more information,
+ * https://www.drupal.org/node/2815083
+ * @preserve
+ */
 /**
  * Generic elements.
  */
@@ -33,7 +39,6 @@ summary,
 .simpletest-results-form summary {
   text-transform: none;
 }
-
 /**
  * Reusable heading classes are included to help modules change the styling of
  * headings on a page without affecting accessibility.
diff --git a/core/themes/seven/css/base/elements.css b/core/themes/seven/css/base/elements.pcss.css
similarity index 100%
copy from core/themes/seven/css/base/elements.css
copy to core/themes/seven/css/base/elements.pcss.css
diff --git a/core/yarn.lock b/core/yarn.lock
index 7396a43fc4..1c922e4363 100644
--- a/core/yarn.lock
+++ b/core/yarn.lock
@@ -426,7 +426,7 @@ atob@^2.1.1:
   resolved "https://registry.yarnpkg.com/atob/-/atob-2.1.2.tgz#6d9517eb9e030d2436666651e86bd9f6f13533c9"
   integrity sha512-Wm6ukoaOGJi/73p/cl2GvLjTI5JM1k/O14isD73YML8StrH/7/lRFgmg8nICZgD3bZZvjwCGxtMOD3wWNAu8cg==
 
-autoprefixer@^9.0.0:
+autoprefixer@^9.0.0, autoprefixer@^9.6.1:
   version "9.6.1"
   resolved "https://registry.yarnpkg.com/autoprefixer/-/autoprefixer-9.6.1.tgz#51967a02d2d2300bb01866c1611ec8348d355a47"
   integrity sha512-aVo5WxR3VyvyJxcJC3h4FKfwCQvQWb1tSI5VHNibddCVWrcD1NvlxEweg3TSgiPztMnWfjpy2FURKA2kvDE+Tw==
@@ -1314,6 +1314,11 @@ color-name@1.1.3:
   resolved "https://registry.yarnpkg.com/color-name/-/color-name-1.1.3.tgz#a7d0558bd89c42f795dd42328f740831ca53bc25"
   integrity sha1-p9BVi9icQveV3UIyj3QIMcpTvCU=
 
+color-name@^1.1.4:
+  version "1.1.4"
+  resolved "https://registry.yarnpkg.com/color-name/-/color-name-1.1.4.tgz#c2a09a87acbde69543de6f63fa3995c826c536a2"
+  integrity sha512-dOy+3AuW3a2wNbZHIuMZpTcgjGuLU/uBL/ubcZF9OXbDo8ff4O8yVp5Bf0efS8uEoYo5q4Fx7dY9OgQGXgAsQA==
+
 combined-stream@^1.0.6, combined-stream@~1.0.6:
   version "1.0.8"
   resolved "https://registry.yarnpkg.com/combined-stream/-/combined-stream-1.0.8.tgz#c3d45a8b34fd730631a110a8a2520682b31d5a7f"
@@ -1426,6 +1431,16 @@ cross-spawn@^6.0.5:
     shebang-command "^1.2.0"
     which "^1.2.9"
 
+css-unit-converter@^1.1.1:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/css-unit-converter/-/css-unit-converter-1.1.1.tgz#d9b9281adcfd8ced935bdbaba83786897f64e996"
+  integrity sha1-2bkoGtz9jO2TW9urqDeGiX9k6ZY=
+
+cssesc@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/cssesc/-/cssesc-2.0.0.tgz#3b13bd1bb1cb36e1bcb5a4dcd27f54c5dcb35703"
+  integrity sha512-MsCAG1z9lPdoO/IUMLSBWBSVxVtJ1395VGIQ+Fc2gNdkQ1hNDnQdw3YhA71WJCBW1vdwA0cAnk/DnW6bqoEUYg==
+
 currently-unhandled@^0.4.1:
   version "0.4.1"
   resolved "https://registry.yarnpkg.com/currently-unhandled/-/currently-unhandled-0.4.1.tgz#988df33feab191ef799a61369dd76c17adf957ea"
@@ -2652,6 +2667,11 @@ ip-regex@^2.1.0:
   resolved "https://registry.yarnpkg.com/ip-regex/-/ip-regex-2.1.0.tgz#fa78bf5d2e6913c911ce9f819ee5146bb6d844e9"
   integrity sha1-+ni/XS5pE8kRzp+BnuUUa7bYROk=
 
+ip-regex@^4.1.0:
+  version "4.1.0"
+  resolved "https://registry.yarnpkg.com/ip-regex/-/ip-regex-4.1.0.tgz#5ad62f685a14edb421abebc2fff8db94df67b455"
+  integrity sha512-pKnZpbgCTfH/1NLIlOduP/V+WRXzC2MOz3Qo8xmxk8C5GudJLgK5QyLVXOSWy3ParAH7Eemurl3xjv/WXYFvMA==
+
 ip@^1.1.5:
   version "1.1.5"
   resolved "https://registry.yarnpkg.com/ip/-/ip-1.1.5.tgz#bdded70114290828c0a039e72ef25f5aaec4354a"
@@ -2830,6 +2850,11 @@ is-number@^3.0.0:
   dependencies:
     kind-of "^3.0.2"
 
+is-number@^7.0.0:
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/is-number/-/is-number-7.0.0.tgz#7535345b896734d5f80c4d06c50955527a14f12b"
+  integrity sha512-41Cifkg6e8TylSpdtTpeLVMqvSBEVzTttHvERD741+pnZ8ANv0004MRL43QKPDlK9cGvNp6NZWZUBlbGXYxxng==
+
 is-obj@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/is-obj/-/is-obj-1.0.1.tgz#3e4729ac1f5fde025cd7d83a896dab9f4f67db0f"
@@ -2905,6 +2930,13 @@ is-typedarray@~1.0.0:
   resolved "https://registry.yarnpkg.com/is-typedarray/-/is-typedarray-1.0.0.tgz#e479c80858df0c1b11ddda6940f96011fcda4a9a"
   integrity sha1-5HnICFjfDBsR3dppQPlgEfzaSpo=
 
+is-url-superb@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/is-url-superb/-/is-url-superb-3.0.0.tgz#b9a1da878a1ac73659047d1e6f4ef22c209d3e25"
+  integrity sha512-3faQP+wHCGDQT1qReM5zCPx2mxoal6DzbzquFlCYJLWyy4WPTved33ea2xFbX37z4NoriEwZGIYhFtx8RUB5wQ==
+  dependencies:
+    url-regex "^5.0.0"
+
 is-url@^1.2.2:
   version "1.2.4"
   resolved "https://registry.yarnpkg.com/is-url/-/is-url-1.2.4.tgz#04a4df46d28c4cff3d73d01ff06abeb318a1aa52"
@@ -3912,7 +3944,7 @@ performance-now@^2.1.0:
   resolved "https://registry.yarnpkg.com/performance-now/-/performance-now-2.1.0.tgz#6309f4e0e5fa913ec1c69307ae364b4b377c9e7b"
   integrity sha1-Ywn04OX6kT7BxpMHrjZLSzd8nns=
 
-pify@^2.0.0:
+pify@^2.0.0, pify@^2.3.0:
   version "2.3.0"
   resolved "https://registry.yarnpkg.com/pify/-/pify-2.3.0.tgz#ed141a6ac043a849ea588498e7dca8b15330e90c"
   integrity sha1-7RQaasBDqEnqWISY59yosVMw6Qw=
@@ -3963,6 +3995,32 @@ posix-character-classes@^0.1.0:
   resolved "https://registry.yarnpkg.com/posix-character-classes/-/posix-character-classes-0.1.1.tgz#01eac0fe3b5af71a2a6c02feabb8c1fef7e00eab"
   integrity sha1-AerA/jta9xoqbAL+q7jB/vfgDqs=
 
+postcss-calc@^7.0.1:
+  version "7.0.1"
+  resolved "https://registry.yarnpkg.com/postcss-calc/-/postcss-calc-7.0.1.tgz#36d77bab023b0ecbb9789d84dcb23c4941145436"
+  integrity sha512-oXqx0m6tb4N3JGdmeMSc/i91KppbYsFZKdH0xMOqK8V1rJlzrKlTdokz8ozUXLVejydRN6u2IddxpcijRj2FqQ==
+  dependencies:
+    css-unit-converter "^1.1.1"
+    postcss "^7.0.5"
+    postcss-selector-parser "^5.0.0-rc.4"
+    postcss-value-parser "^3.3.1"
+
+postcss-custom-properties@^9.0.2:
+  version "9.0.2"
+  resolved "https://registry.yarnpkg.com/postcss-custom-properties/-/postcss-custom-properties-9.0.2.tgz#091aefaa309826302d53ec6d780fbe1df8f40fd4"
+  integrity sha512-WHaQrEp3gJ6mgxBA4mGJKW6DSVfy2IFnKPFAb2IEulgxGUW8nWp1NkOD/rWR6e2uIuAdnTa0LXSupST7daniAw==
+  dependencies:
+    postcss "^7.0.17"
+    postcss-values-parser "^3.0.5"
+
+postcss-header@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/postcss-header/-/postcss-header-1.0.0.tgz#36bc650f6f841db86558bd5c66461545d9f413ef"
+  integrity sha512-YUcU2oHQNsNVUDPdQg6/TXBWvI7dBGf2bsLQdVlLiLM5kiGLGCcszYDlVTaicmXpKANdS1T7bxpJtCacrMButw==
+  dependencies:
+    babel-register "^6.26.0"
+    postcss "^6.0.13"
+
 postcss-html@^0.36.0:
   version "0.36.0"
   resolved "https://registry.yarnpkg.com/postcss-html/-/postcss-html-0.36.0.tgz#b40913f94eaacc2453fd30a1327ad6ee1f88b204"
@@ -3970,6 +4028,16 @@ postcss-html@^0.36.0:
   dependencies:
     htmlparser2 "^3.10.0"
 
+postcss-import@^12.0.1:
+  version "12.0.1"
+  resolved "https://registry.yarnpkg.com/postcss-import/-/postcss-import-12.0.1.tgz#cf8c7ab0b5ccab5649024536e565f841928b7153"
+  integrity sha512-3Gti33dmCjyKBgimqGxL3vcV8w9+bsHwO5UrBawp796+jdardbcFl4RP5w/76BwNL7aGzpKstIfF9I+kdE8pTw==
+  dependencies:
+    postcss "^7.0.1"
+    postcss-value-parser "^3.2.3"
+    read-cache "^1.0.0"
+    resolve "^1.1.7"
+
 postcss-jsx@^0.36.0:
   version "0.36.3"
   resolved "https://registry.yarnpkg.com/postcss-jsx/-/postcss-jsx-0.36.3.tgz#c91113eae2935a1c94f00353b788ece9acae3f46"
@@ -4062,6 +4130,15 @@ postcss-selector-parser@^3.1.0:
     indexes-of "^1.0.1"
     uniq "^1.0.1"
 
+postcss-selector-parser@^5.0.0-rc.4:
+  version "5.0.0"
+  resolved "https://registry.yarnpkg.com/postcss-selector-parser/-/postcss-selector-parser-5.0.0.tgz#249044356697b33b64f1a8f7c80922dddee7195c"
+  integrity sha512-w+zLE5Jhg6Liz8+rQOWEAwtwkyqpfnmsinXjXg6cY7YIONZZtgvE0v2O0uhQBs0peNomOJwWRKt6JBfTdTd3OQ==
+  dependencies:
+    cssesc "^2.0.0"
+    indexes-of "^1.0.1"
+    uniq "^1.0.1"
+
 postcss-sorting@^4.1.0:
   version "4.1.0"
   resolved "https://registry.yarnpkg.com/postcss-sorting/-/postcss-sorting-4.1.0.tgz#a107f0bf3852977fa64e4442bc340c88d5aacdb3"
@@ -4075,7 +4152,7 @@ postcss-syntax@^0.36.2:
   resolved "https://registry.yarnpkg.com/postcss-syntax/-/postcss-syntax-0.36.2.tgz#f08578c7d95834574e5593a82dfbfa8afae3b51c"
   integrity sha512-nBRg/i7E3SOHWxF3PpF5WnJM/jQ1YpY9000OaVXlAQj6Zp/kIqJxEDWIZ67tAd7NLuk7zqN4yqe9nc0oNAOs1w==
 
-postcss-value-parser@^3.3.0:
+postcss-value-parser@^3.2.3, postcss-value-parser@^3.3.0, postcss-value-parser@^3.3.1:
   version "3.3.1"
   resolved "https://registry.yarnpkg.com/postcss-value-parser/-/postcss-value-parser-3.3.1.tgz#9ff822547e2893213cf1c30efa51ac5fd1ba8281"
   integrity sha512-pISE66AbVkp4fDQ7VHBwRNXzAAKJjw4Vw7nWI/+Q3vuly7SNfgYXvm6i5IgFylHGK5sP/xHAbB7N49OS4gWNyQ==
@@ -4085,6 +4162,17 @@ postcss-value-parser@^4.0.0:
   resolved "https://registry.yarnpkg.com/postcss-value-parser/-/postcss-value-parser-4.0.2.tgz#482282c09a42706d1fc9a069b73f44ec08391dc9"
   integrity sha512-LmeoohTpp/K4UiyQCwuGWlONxXamGzCMtFxLq4W1nZVGIQLYvMCJx3yAF9qyyuFpflABI9yVdtJAqbihOsCsJQ==
 
+postcss-values-parser@^3.0.5:
+  version "3.0.5"
+  resolved "https://registry.yarnpkg.com/postcss-values-parser/-/postcss-values-parser-3.0.5.tgz#9f83849fb89eaac74c2d5bf75e8e9715508a8c8d"
+  integrity sha512-0N6EUBx2Vzl0c9LQipuus90EkVh7saBQFRhgAYpHHcDCIvxRt+K/q0zwcIYtDQVNs5Y9NGqei4AuCEvAOsePfQ==
+  dependencies:
+    color-name "^1.1.4"
+    is-number "^7.0.0"
+    is-url-superb "^3.0.0"
+    postcss "^7.0.5"
+    url-regex "^5.0.0"
+
 postcss@^5.0.0, postcss@^5.0.18:
   version "5.2.18"
   resolved "https://registry.yarnpkg.com/postcss/-/postcss-5.2.18.tgz#badfa1497d46244f6390f58b319830d9107853c5"
@@ -4095,6 +4183,15 @@ postcss@^5.0.0, postcss@^5.0.18:
     source-map "^0.5.6"
     supports-color "^3.2.3"
 
+postcss@^6.0.13:
+  version "6.0.23"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-6.0.23.tgz#61c82cc328ac60e677645f979054eb98bc0e3324"
+  integrity sha512-soOk1h6J3VMTZtVeVpv15/Hpdl2cBLX3CAw4TAbkpTJiNPk9YP/zWcD1ND+xEtvyuuvKzbxliTOIyvkSeSJ6ag==
+  dependencies:
+    chalk "^2.4.1"
+    source-map "^0.6.1"
+    supports-color "^5.4.0"
+
 postcss@^7.0.0, postcss@^7.0.1, postcss@^7.0.13, postcss@^7.0.14, postcss@^7.0.17, postcss@^7.0.2, postcss@^7.0.7:
   version "7.0.17"
   resolved "https://registry.yarnpkg.com/postcss/-/postcss-7.0.17.tgz#4da1bdff5322d4a0acaab4d87f3e782436bad31f"
@@ -4104,6 +4201,15 @@ postcss@^7.0.0, postcss@^7.0.1, postcss@^7.0.13, postcss@^7.0.14, postcss@^7.0.1
     source-map "^0.6.1"
     supports-color "^6.1.0"
 
+postcss@^7.0.18, postcss@^7.0.5:
+  version "7.0.18"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-7.0.18.tgz#4b9cda95ae6c069c67a4d933029eddd4838ac233"
+  integrity sha512-/7g1QXXgegpF+9GJj4iN7ChGF40sYuGYJ8WZu8DZWnmhQ/G36hfdk3q9LBJmoK+lZ+yzZ5KYpOoxq7LF1BxE8g==
+  dependencies:
+    chalk "^2.4.2"
+    source-map "^0.6.1"
+    supports-color "^6.1.0"
+
 prelude-ls@~1.1.2:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/prelude-ls/-/prelude-ls-1.1.2.tgz#21932a549f5e52ffd9a827f570e04be62a97da54"
@@ -4212,6 +4318,13 @@ react-is@^16.8.1:
   resolved "https://registry.yarnpkg.com/react-is/-/react-is-16.9.0.tgz#21ca9561399aad0ff1a7701c01683e8ca981edcb"
   integrity sha512-tJBzzzIgnnRfEm046qRcURvwQnZVXmuCbscxUO5RWrGTXpon2d4c8mI0D8WE6ydVIm29JiLB6+RslkIvym9Rjw==
 
+read-cache@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/read-cache/-/read-cache-1.0.0.tgz#e664ef31161166c9751cdbe8dbcf86b5fb58f774"
+  integrity sha1-5mTvMRYRZsl1HNvo28+GtftY93Q=
+  dependencies:
+    pify "^2.3.0"
+
 read-file-stdin@^0.2.1:
   version "0.2.1"
   resolved "https://registry.yarnpkg.com/read-file-stdin/-/read-file-stdin-0.2.1.tgz#25eccff3a153b6809afacb23ee15387db9e0ee61"
@@ -4491,7 +4604,7 @@ resolve-url@^0.2.1:
   resolved "https://registry.yarnpkg.com/resolve-url/-/resolve-url-0.2.1.tgz#2c637fe77c893afd2a663fe21aa9080068e2052a"
   integrity sha1-LGN/53yJOv0qZj/iGqkIAGjiBSo=
 
-resolve@^1.10.0, resolve@^1.10.1, resolve@^1.11.0, resolve@^1.3.2, resolve@^1.5.0:
+resolve@^1.1.7, resolve@^1.10.0, resolve@^1.10.1, resolve@^1.11.0, resolve@^1.3.2, resolve@^1.5.0:
   version "1.12.0"
   resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.12.0.tgz#3fc644a35c84a48554609ff26ec52b66fa577df6"
   integrity sha512-B/dOmuoAik5bKcD6s6nXDCjzUKnaDvdkRyAk6rsmsKLipWj4797iothd7jmmUhWTfinVMU+wc56rYKsit2Qy4w==
@@ -5027,7 +5140,7 @@ supports-color@^3.2.3:
   dependencies:
     has-flag "^1.0.0"
 
-supports-color@^5.3.0:
+supports-color@^5.3.0, supports-color@^5.4.0:
   version "5.5.0"
   resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-5.5.0.tgz#e2e69a44ac8772f78a1ec0b35b689df6530efc8f"
   integrity sha512-QjVjwdXIt408MIiAqCX4oUKsgU2EqAGzs2Ppkm4aQYbjm+ZEWEcW4SfFNTr4uMNZma0ey4f5lgLrkB0aX0QMow==
@@ -5104,6 +5217,11 @@ thunkify@^2.1.2:
   resolved "https://registry.yarnpkg.com/thunkify/-/thunkify-2.1.2.tgz#faa0e9d230c51acc95ca13a361ac05ca7e04553d"
   integrity sha1-+qDp0jDFGsyVyhOjYawFyn4EVT0=
 
+tlds@^1.203.0:
+  version "1.203.1"
+  resolved "https://registry.yarnpkg.com/tlds/-/tlds-1.203.1.tgz#4dc9b02f53de3315bc98b80665e13de3edfc1dfc"
+  integrity sha512-7MUlYyGJ6rSitEZ3r1Q1QNV8uSIzapS8SmmhSusBuIc7uIxPPwsKllEP0GRp1NS6Ik6F+fRZvnjDWm3ecv2hDw==
+
 tmp@^0.0.33:
   version "0.0.33"
   resolved "https://registry.yarnpkg.com/tmp/-/tmp-0.0.33.tgz#6d34335889768d21b2bcda0aa277ced3b1bfadf9"
@@ -5318,6 +5436,14 @@ urix@^0.1.0:
   resolved "https://registry.yarnpkg.com/urix/-/urix-0.1.0.tgz#da937f7a62e21fec1fd18d49b35c2935067a6c72"
   integrity sha1-2pN/emLiH+wf0Y1Js1wpNQZ6bHI=
 
+url-regex@^5.0.0:
+  version "5.0.0"
+  resolved "https://registry.yarnpkg.com/url-regex/-/url-regex-5.0.0.tgz#8f5456ab83d898d18b2f91753a702649b873273a"
+  integrity sha512-O08GjTiAFNsSlrUWfqF1jH0H1W3m35ZyadHrGv5krdnmPPoxP27oDTqux/579PtaroiSGm5yma6KT1mHFH6Y/g==
+  dependencies:
+    ip-regex "^4.1.0"
+    tlds "^1.203.0"
+
 use@^3.1.0:
   version "3.1.1"
   resolved "https://registry.yarnpkg.com/use/-/use-3.1.1.tgz#d50c8cac79a19fbc20f2911f56eb973f4e10070f"