Add some linking for hw vids (#1813)

* add linking for hw vids, fix card pages

* revert vid card page and inline youtube links

docs/device.md

@@ -20,6 +20,11 @@ They can be set to on/off and the brightness can be controlled.
 The yellow light on the back of the micro:bit is the status LED.
 It flashes yellow when the system wants to tell the user that something has happened.
 
+See how the @boardname@ shows numbers, text, and displays images by watching this video about LEDs:
+
+https://www.youtube.com/watch?v=qqBmvHD5bCw
+
+
 ## Buttons
 
 Buttons A and B are a form of input.  When you press a button, it completes an electrical circuit. 
@@ -29,6 +34,10 @@ to act on these events.
 Button R on the back of the micro:bit is a system button. It has different uses. 
 When you have downloaded and run your code onto your micro:bit, press Button R to restart and run your program from the beginning.
 
+Find out how buttons provide input to the @boardname@ in this video:
+
+https://www.youtube.com/watch?v=t_Qujjd_38o
+
 ## USB connection
 
 When you plug in your micro:bit via [USB](/device/usb), it should appear as  a ``MICROBIT`` drive. 
@@ -62,6 +71,10 @@ There is an accelerometer on your micro:bit which detects changes in the micro:b
 It converts analogue information into digital form that can be used in micro:bit programs. 
 Output is in milli-g. The device will also detect a small number of standard actions e.g. shake, tilt and free-fall.
 
+Watch this video to learn how the accelerometer works:
+
+https://www.youtube.com/watch?v=byngcwjO51U
+
 ## Pins
 
 The [pins](/device/pins) can be a form of electrical input or output. 
@@ -71,6 +84,18 @@ There are labels for the input/output pins ``P0``, ``P1``, ``P2``, which you can
 
 The screen can also be used a light level sensor (it's a really cool trick).
 
+Learn more about how light level is detected in this light sensor video:
+
+https://www.youtube.com/watch?v=TKhCr-dQMBY
+
+## Temperature
+
+Temperatrue is measured on the @boardname@ by detecting how hot its physical CPU material is. Since it operates nearly as cool as the air around it, the temperature it measures for itself is a good approximation for the ambient temperature (the temperature near and around it).
+
+See how the @boardname@ can detect hot or cold in this temperature sensing video:
+
+https://www.youtube.com/watch?v=_T4N8O9xsMA
+
 ## Runtime
 
 The micro:bit embodies many fundamental concepts in computer science. To learn more, read [the micro:bit - a reactive system](/device/reactive).

docs/reference/basic/show-leds.md

@@ -19,6 +19,12 @@ basic.showLeds(`
 * `interval` is an optional [number](/types/number) that means how many milliseconds to wait after showing a picture.
 If you are programming with blocks, `interval` is set at 400 milliseconds.
 
+## ~ hint
+
+See how the @boardname@ shows numbers, text, and displays images by watching this video about [LEDs](https://www.youtube.com/watch?v=qqBmvHD5bCw).
+
+## ~
+
 ## Example
 
 This program shows a picture with the ``show leds`` function.

docs/reference/input/acceleration.md

@@ -15,6 +15,10 @@ A **g** is as much acceleration as you get from Earth's gravity.
 
 ## ~
 
+Watch this video to learn how the accelerometer on the @boardname@ works:
+
+https://www.youtube.com/watch?v=byngcwjO51U
+
 ## Parameters
 
 * **dimension**: the direction you are checking for acceleration, or the total strength of force.

docs/reference/input/button-is-pressed.md

@@ -12,11 +12,11 @@ input.buttonIsPressed(Button.A);
 
 ## Returns
 
-* [Boolean](/blocks/logic/boolean) that is `true` if the button you are checking is pressed, `false` if it is not pressed.
+* a [boolean](/blocks/logic/boolean) value that is `true` if the button you are checking is pressed, `false` if it is not pressed.
 
 ## Example
 
-This program uses an [if](/blocks/logic/if) to run 
+This program uses an [``||logic:if||``](/blocks/logic/if) to run 
 one part of the program if the `A` button is pressed, and 
 another part if it is not pressed.
 
@@ -25,14 +25,18 @@ basic.forever(() => {
     let pressed = input.buttonIsPressed(Button.A)
     if (pressed) {
         // this part runs if the A button is pressed
-        basic.showNumber(1, 150)
+        basic.showNumber(1)
     } else {
         // this part runs if the A button is *not* pressed
-        basic.showNumber(0, 150)
+        basic.showNumber(0)
     }
 })
 ```
 
+Find out how buttons provide input to the @boardname@ in this video:
+
+https://www.youtube.com/watch?v=t_Qujjd_38o
+
 ## See also
 
 [on button pressed](/reference/input/on-button-pressed), [if](/blocks/logic/if), [forever](/reference/basic/forever)

docs/reference/input/light-level.md

@@ -14,6 +14,10 @@ has to be turned on first.
 input.lightLevel();
 ```
 
+Learn more about how light level is detected in this light sensor video:
+
+https://www.youtube.com/watch?v=TKhCr-dQMBY.
+
 ## Returns
 
 * a [Number](/types/number) that means a light level from ``0`` (dark) to ``255`` (bright).

docs/reference/input/on-button-pressed.md

@@ -12,6 +12,10 @@ on the @boardname@.
 input.onButtonPressed(Button.A, () => {})
 ```
 
+Find out how buttons provide input to the @boardname@ in this video:
+
+https://www.youtube.com/watch?v=t_Qujjd_38o
+
 ## Example: count button clicks
 
 This example counts how many times you press the `A` button. 

docs/reference/input/rotation.md

@@ -9,7 +9,9 @@ input.rotation(Rotation.Roll);
 ## ~hint
 
 The @boardname@ has a part called the **accelerometer** that can
-check how the @boardname@ is moving.
+check how the @boardname@ is moving. Watch this video to learn how the accelerometer works:
+
+https://www.youtube.com/watch?v=byngcwjO51U
 
 ## ~
 

docs/reference/input/temperature.md

@@ -9,7 +9,7 @@ input.temperature();
 
 ## Returns
 
-* a [Number](/types/number) that means the Celsius temperature.
+* a [number](/types/number) that is the temperature in degrees Celsius.
 
 ## How does it work?
 
@@ -18,6 +18,11 @@ Because the @boardname@ does not usually get very hot, the temperature of the CP
 is usually close to the temperature of wherever you are.
 The @boardname@ might warm up a little if you make it work hard, though!
 
+Learn more about how the @boardname@ can detect hot or cold in this video:
+
+https://www.youtube.com/watch?v=_T4N8O9xsMA
+
+
 ## Example: @boardname@ thermometer
 
 The following example uses `temperature` and `show number` to show the temperature of the room.

docs/reference/led.md

@@ -12,16 +12,11 @@ led.plotBrightness(0, 0, 255)
 led.setBrightness(255);
 led.stopAnimation();
 led.plotBarGraph(0, 0);
-led.fadeIn();
-led.fadeOut();
-led.plotAll();
-led.screenshot();
-led.toggleAll();
 led.setDisplayMode(DisplayMode.BackAndWhite);
 led.enable(false)
 ```
 
 ## See Also
 
-[plot](/reference/led/plot), [unplot](/reference/led/unplot), [point](/reference/led/point), [brightness](/reference/led/brightness), [setBrightness](/reference/led/set-brightness), [stopAnimation](/reference/led/stop-animation), [plotBarGraph](/reference/led/plot-bar-graph), [fadeIn](/reference/led/fade-in), [fadeOut](/reference/led/fade-out), [plotAll](/reference/led/plot-all), [screenshot](/reference/led/screenshot), [toggle](/reference/led/toggle), [toggleAll](/reference/led/toggle-all), [setDisplayMode](/reference/led/set-display-mode), [enabled](/reference/led/enable),
+[plot](/reference/led/plot), [unplot](/reference/led/unplot), [point](/reference/led/point), [brightness](/reference/led/brightness), [setBrightness](/reference/led/set-brightness), [stopAnimation](/reference/led/stop-animation), [plotBarGraph](/reference/led/plot-bar-graph), [toggle](/reference/led/toggle), [setDisplayMode](/reference/led/set-display-mode), [enabled](/reference/led/enable),
 [plotBrightness](/reference/led/plot-brightness),