diff --git a/git-diff-flex.css b/git-diff-flex.css
new file mode 100644
index 0000000..4dd8877
--- /dev/null
+++ b/git-diff-flex.css
@@ -0,0 +1,19 @@
+.gdf-handle {
+    position: absolute;
+    width: 3px;
+    background-color: #4569ad;
+    cursor: col-resize;
+}
+
+.gdf-handle:hover {
+    border: 1px solid #4569ad;
+    background-color: #5b8ae0;
+}
+
+.gdf-hidden {
+    display: none;
+}
+
+.gdf-parent:hover .gdf-handle {
+    display: block;
+}
diff --git a/git-diff-flex.js b/git-diff-flex.js
new file mode 100644
index 0000000..d7c4a55
--- /dev/null
+++ b/git-diff-flex.js
@@ -0,0 +1,164 @@
+(function(window, document) {
+
+  let tableKey = 'gdfTable'
+  let tableHeightKey = 'gdfTableHeight'
+  let classes = {
+    current: 'gdf-current',
+    handle: 'gdf-handle',
+    hidden: 'gdf-hidden',
+    table: 'gdf-table',
+    drag: 'gdf-drag'
+  };
+
+  const handle = generateHandle();
+
+  // The main program... just mark the tables
+  findTables();
+
+  /**
+   * Recalculate the handle on window resize.
+   */
+  window.addEventListener('resize', calculateHandlePosition);
+
+  /**
+   * Mark the handle as 'undraggable' on mouse up.
+   */
+  document.body.addEventListener('mouseup', function () {
+    handle.classList.remove(classes.drag);
+  });
+
+  /**
+   * Recalculate the handle when the table height changes on mouse move.
+   */
+  document.body.addEventListener('mousemove', function () {
+    let table = getCurrentTable();
+    if (table && handle.classList.contains(classes.drag)) {
+      let height = table.getBoundingClientRect().height;
+      if (this.dataset[tableHeightKey] != height) {
+        this.dataset[tableHeightKey] = height;
+        calculateHandlePosition();
+      }
+    }
+  });
+
+  /**
+   * Move the handle and the table columns on mouse move.
+   */
+  document.body.addEventListener('mousemove', function (e) {
+    let table = getCurrentTable();
+    if (table && handle.classList.contains(classes.drag)) {
+
+      // Set the current position
+      let colPos = table.querySelector('td.blob-num-deletion').getBoundingClientRect();
+      let col = table.querySelector('colgroup>col:nth-child(2)');
+      let rect = handle.getBoundingClientRect();
+      let capLeft = colPos.right + colPos.width + 100;
+      let capRight = table.querySelector('tbody').getBoundingClientRect().right
+        - table.querySelector('td.blob-num-addition').getBoundingClientRect().width
+        - 100;
+
+      // Move first... ask questions later!
+      handle.style.left = e.clientX + 'px';
+      col.style.width = (rect.left - colPos.right + 1) + 'px';
+
+      // Stop moving if over the right cap
+      if (e.clientX > capRight) {
+        handle.style.left = capRight + 'px';
+        col.style.width = (capRight - colPos.left + 1) + 'px';
+      }
+
+      // Stop moving if over the left cap
+      if (e.clientX < capLeft) {
+        handle.style.left = capLeft + 'px';
+        col.style.width = (capLeft - colPos.right + 1) + 'px';
+      }
+    }
+  });
+
+  /**
+   * Find all diff tables.
+   */
+  function findTables() {
+    return [].map.call(document.querySelectorAll('table.diff-table.file-diff-split'), (table, i) => {
+      table.classList.add(classes.table);
+      table.dataset[tableKey] = i;
+      table.addEventListener('mouseenter', showHandle);
+      table.addEventListener('mouseleave', hideHandle);
+      return table;
+    });
+  }
+
+  /**
+   * Get the current table the mouse is over.
+   */
+  function getCurrentTable() {
+    return document.querySelector(`.${classes.current}`);
+  }
+
+  /**
+   * On table enter, mark as current, show the handle to the user, and recalculate position.
+   */
+  function showHandle() {
+    this.classList.add(classes.current);
+    handle.dataset[tableKey] = this.dataset[tableKey];
+    handle.classList.remove(classes.hidden);
+    calculateHandlePosition();
+  }
+
+  /**
+   * On table leave, remove the current class and hide the handle from the user.
+   */
+  function hideHandle() {
+    this.classList.remove(classes.current);
+    handle.classList.add(classes.hidden);
+  }
+
+  /**
+   * Calculate the handle's position, relative to the table's center column.
+   */
+  function calculateHandlePosition() {
+    let table = getCurrentTable();
+    if (table) {
+      let bodyRect = document.body.getBoundingClientRect();
+      let tableRect = table.getBoundingClientRect();
+      let top = tableRect.top - bodyRect.top;
+      let centerColRect = table.querySelector('td.blob-num-addition').getBoundingClientRect();
+
+      handle.style.height = tableRect.height + 'px';
+      handle.style.left = (centerColRect.left - 1) + 'px';
+      handle.style.top = top + 'px';
+    }
+  }
+
+  /**
+   * Create the handle singleton and append it to the DOM.
+   */
+  function generateHandle() {
+    let handle = document.createElement('div');
+    handle.classList.add(classes.handle);
+    handle.classList.add(classes.hidden);
+    handle.dataset[tableHeightKey] = 0;
+
+    handle.onmousedown = function (e) {
+      e.preventDefault();
+      this.classList.add(classes.drag);
+    };
+
+    handle.onmouseup = function () {
+      this.classList.remove(classes.drag);
+    };
+
+    handle.onmouseenter = function () {
+      this.classList.remove(classes.hidden);
+    };
+
+    handle.onmouseleave = function () {
+      this.classList.add(classes.hidden);
+    };
+
+    document.body.appendChild(handle);
+
+    return handle;
+  }
+
+})(window, document);
diff --git a/manifest.json b/manifest.json
new file mode 100644
index 0000000..8e532af
--- /dev/null
+++ b/manifest.json
@@ -0,0 +1,27 @@
+{
+  "name": "Git Diff Flex",
+  "version": "1.0.0",
+  "description": "Git Diff Flex adds a draggable pane bezel between two files when comparing diffs! Currently only for github.com.",
+  "permissions": [
+    "activeTab",
+    "declarativeContent",
+    "storage"
+  ],
+  "page_action": {
+    "default_popup": "popup.html"
+  },
+  "content_scripts": [
+    {
+      "matches": [
+        "*://*.github.com/*"
+      ],
+      "css": [
+        "git-diff-flex.css"
+      ],
+      "js": [
+        "git-diff-flex.js"
+      ]
+    }
+  ],
+  "manifest_version": 2
+}