Add some linking for hw vids (#1813)

* add linking for hw vids, fix card pages

* revert vid card page and inline youtube links

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.