Merge pull request #74 from alan412/pr_design_docs

Start of design doc

Author: lizlooney

docs/design.md

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+# Overarching thoughts (North Star)
+* The primary purpose for Blocks is to be an easier environment for students to program robots.
+    * Students should be able to program in Blocks without any experienced software mentor help.
+    * This means that reducing confusion in blocks is more important than being 1:1 mapping to Python
+    * For ease of use, we are ok with not being able to do everything in Blocks you can do in Python.
+* You should be able to make a competitive robot using Blocks
+    * Our goal is to raise the floor, not lower the ceiling
+* Programming in Blocks is still programming.   You can make logic errors and programs that don't work and have errors
+* Some students will move on from Blocks to text based languages
+    * Students who want to do more than they can in Blocks can export from Blocks and use that as a starting point for their own Python coding.
+
+# Intentional Limitations (for simplicity)
+* Each blockly workspace goes to one Python file (module) and can only contain one class
+* The only type of methods that can be created are class instance methods
+* All variables created in blockly will be class instance variables
+
+# Design thoughts
+(We assume that these bullet points apply to programming in C++, Java, and Python too.)
+## OpModes
+* An OpMode can be either Autonomous or Teleop
+* An OpMode can be marked as Disabled or Enabled
+* An OpMode has access to a singleton instance of the Robot class
+## Robot
+* There should be one robot class that is shared between all OpModes
+* A robot has zero or more mechanisms 
+* A Robot has zero or more components
+
+## Mechanisms
+* A mechansim can be created by the student and can have zero or more submechanisms and zero or more components
+* Example:  A claw could have a servo (to open and close) and a range sensor (to determine when something is in the claw)
+
+## Components
+* Every actuator is a component
+* Every sensor is a component