add draft roadmap

docs/roadmap.md

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+# Uitschrijven 'design' calculator
+
+
+Als uiteindelijk doel wil ik graag een spelletje tot uitkomst laten komen, in vergelijking met:
+
+https://play.google.com/store/apps/details?id=com.sm.calculateme
+
+
+Op die manier zou je dus een aantal componenten hebben:
+
+
+1. tonen 'battery level'
+2. tonen actieve getal
+3. tonen doel getal
+4. een panel hebben waar knoppen op toegevoegd kunnen worden
+5. elke knop is in feite het aftrappen van een command chain op het huidige
+   resultaat.
+
+Voorbeeld:
+
+```
+Battery: [▓▓▓░░░░]
+Display: [      5]
+Goal: 125
+
+Buttons:
+┌────────────────┐
+│ 1. (* 10, + 5) │
+│ 2. (+ 10, * 2) │
+│ 3. - 5         │
+│ 4. Undo        │
+└────────────────┘
+
+Your choice: (1 - 4):
+
+```
+
+Elke button is dus in feite een 'command chain' die uitgevoerd wordt.
+
+De code van een level zou dus zoiets kunnen zijn:
+
+```js
+let level = new Level();
+level.setInitialResult(0);
+level.setBatteryPower(3); // amount of 'moves'
+
+let commandChain = new CommandChain() // ?
+commandChain.times(10)
+commandChain.add(5)
+level.addButton(0, commandChain)
+
+// ... other buttons
+
+level.start() // ?
+
+```
+
+## To get there
+
+Stories, backlog
+
+1. Calculation operators (add, multiply, square, subtract)
+
+  - Setup, TDD cycle, refactoring
+
+2. Chain operations and see result
+
+  - Objects, getters, privacy of object data
+
+3. Undo operations
+
+  - Lazy evaluation, spying, stubbing
+
+4. As a user I want to see the result of my formula on the screen
+
+  See result on display -> Interface
+
+  - Interfaces / Ducktyping, separation of concerns, single responsibility
+
+5. As user I want to manipulate the result using basic commands/operations
+
+  Customize commands. (use simple commands with single operation, +3, *5, etc)
+
+6. As User I want to get feedback when I reached the set goal.
+
+7. As User I want to receive feedback if I do not reach the set goal within the allowed amount of moves.
+
+  Add battery. Each execute drains the battery.
+
+  - This element turns it into a game, because a goal and lose scenario is added. But it hardly changes the core mechanics we established earlier
+
+
+8. As a user I want to append a number to the existing result
+
+  - Scaling up architecture (instead of commands in a chain, we go from chains in a chain as well) 
+
+9. Create single level
+
+  - Wrap up. Also thinking about: How to seperate code from content? (level contents, multiple levels)
+
+  > when every goes well, there should not be a lot of code for a nice functional game. This is also the perfect moment to discuss how a developer spends its time between thinking and actually writing code. This is a nice stepping stone to discuss the value of Pair programming.
+
+### Topics not yet covered:
+
+- Promises / Asynchronity
+- Regex
+- Exceptions
+- Immutability