minor

1-js/04-object-basics/03-symbol/article.md

@@ -52,7 +52,7 @@ alert(id); // TypeError: Cannot convert a Symbol value to a string
 
 That's a "language guard" against messing up, because strings and symbols are fundamentally different and should not occasionally convert one into another.
 
-If we really want to show a symbol, we need to call `.toString()` on it, like here:
+If we really want to show a symbol, we need to explicitly call `.toString()` on it, like here:
 ```js run
 let id = Symbol("id");
 *!*
@@ -60,7 +60,7 @@ alert(id.toString()); // Symbol(id), now it works
 */!*
 ```
 
-Or get `symbol.description` property to get the description only:
+Or get `symbol.description` property to show the description only:
 ```js run
 let id = Symbol("id");
 *!*
@@ -133,7 +133,7 @@ let id = Symbol("id");
 let user = {
   name: "John",
 *!*
-  [id]: 123 // not just "id: 123"
+  [id]: 123 // not "id: 123"
 */!*
 };
 ```

2-ui/3-event-details/4-mouse-drag-and-drop/1-slider/solution.md

@@ -1,4 +1,5 @@
+As we can see from HTML/CSS, the slider is a `<div>` with a colored background, that contains a runner -- another `<div>` with `position:relative`.
 
-We have a horizontal Drag'n'Drop here.
+To position the runner we use `position:relative`, to provide the coordinates relative to its parent, here it's more convenient here than `position:absolute`.
 
-To position the element we use `position:relative` and slider-relative coordinates for the thumb. Here it's more convenient here than `position:absolute`.
+Then we implement horizontal-only Drag'n'Drop with limitation by width.

2-ui/3-event-details/4-mouse-drag-and-drop/2-drag-heroes/solution.md

@@ -1,5 +1,5 @@
-To drag the element we can use `position:fixed`, it makes coordinates easier to manage. At the end we should switch it back to `position:absolute`.
+To drag the element we can use `position:fixed`, it makes coordinates easier to manage. At the end we should switch it back to `position:absolute` to lay the element into the document.
 
-Then, when coordinates are at window top/bottom, we use `window.scrollTo` to scroll it.
+When coordinates are at window top/bottom, we use `window.scrollTo` to scroll it.
 
 More details in the code, in comments.

2-ui/3-event-details/4-mouse-drag-and-drop/2-drag-heroes/task.md

@@ -12,8 +12,8 @@ Requirements:
 
 - Use event delegation to track drag start: a single event handler on `document` for `mousedown`.
 - If elements are dragged to top/bottom window edges -- the page scrolls up/down to allow further dragging.
-- There is no horizontal scroll.
+- There is no horizontal scroll (this makes the task a bit simpler, adding it is easy).
-- Draggable elements should never leave the window, even after swift mouse moves.
+- Draggable elements or their parts should never leave the window, even after swift mouse moves.
 
 The demo is too big to fit it here, so here's the link.
 

2-ui/3-event-details/4-mouse-drag-and-drop/article.md

@@ -241,7 +241,7 @@ An extended code of `onMouseMove` to find "droppable" elements:
 
 ```js
 // potential droppable that we're flying over right now
-let currentDroppable = null; 
+let currentDroppable = null;
 
 function onMouseMove(event) {
   moveAt(event.pageX, event.pageY);
@@ -251,13 +251,13 @@ function onMouseMove(event) {
   ball.hidden = false;
 
   // mousemove events may trigger out of the window (when the ball is dragged off-screen)
-  // if clientX/clientY are out of the window, then elementfromPoint returns null
+  // if clientX/clientY are out of the window, then elementFromPoint returns null
   if (!elemBelow) return;
 
   // potential droppables are labeled with the class "droppable" (can be other logic)
   let droppableBelow = elemBelow.closest('.droppable');
 
-  if (currentDroppable != droppableBelow) { // if there are any changes
+  if (currentDroppable != droppableBelow) {
     // we're flying in or out...
     // note: both values can be null
     //   currentDroppable=null if we were not over a droppable before this event (e.g over an empty space)
@@ -288,13 +288,13 @@ We considered a basic Drag'n'Drop algorithm.
 
 The key components:
 
-1. Events flow: `ball.mousedown` -> `document.mousemove` -> `ball.mouseup` (cancel native `ondragstart`).
+1. Events flow: `ball.mousedown` -> `document.mousemove` -> `ball.mouseup` (don't forget to cancel native `ondragstart`).
 2. At the drag start -- remember the initial shift of the pointer relative to the element: `shiftX/shiftY` and keep it during the dragging.
 3. Detect droppable elements under the pointer using `document.elementFromPoint`.
 
 We can lay a lot on this foundation.
 
-- On `mouseup` we can finalize the drop: change data, move elements around.
+- On `mouseup` we can intellectually finalize the drop: change data, move elements around.
 - We can highlight the elements we're flying over.
 - We can limit dragging by a certain area or direction.
 - We can use event delegation for `mousedown/up`. A large-area event handler that checks  `event.target` can manage Drag'n'Drop for hundreds of elements.