removed some constraints on quiz (uniqueness of puzzles, number of bits etc), added animation when the answer is wrong

TODO.md

@@ -1,35 +1,56 @@
-- add progression
-- add explanation/tutorial
-- timed
-- add column labels
-- add spacing beyond X places
-- add color and font
-- optional super mario tyype sounds
-- gamification via character upgrades
+# Content
+- explanation/tutorial
+- 'about'/contact
+
+## Curriculum
+- how to negate a signed binary integer?
+- how to convert decimal to binary?
+- how to convert hex to binary?
+- how to convert binary to hex?
+- how many unsigned integers can be represented in ____? (a byte, nibble, word)
+- how many _signed_ integers can be represented in ____? (a byte, nibble, word)
+- how to determine if a binary int is even/odd?
+- what can be said of a binary integer who ____ bits are 0?
+- if all positions in a binary integer are 0 except position ____, what number does it represent?
+- if all positions in a binary integer are 1 except position ____, what number does it represent?
+- memorize powers of 2 up to 16 (speed round)
+- what happens to the represented integer after shifting to the left?
+- what happens to the represented integer after shifting to the right?
+- what is the binary for the value 2^n - 1?
+- what is sign extension? how do you do it?
+- what is contraction?
+- what is zero extension?
+
+# Design
+- color and font
+- toggleable column labels
+- animations
+  - [x] 'nuh-uh' shake for wrong answers
+  - [ ] nice reward animations for right answers
+  - [ ] make the placeholders become real text for a split second before starting
 - processor graphic/animation
   - diff processors for different bits
-- mobile
+
+## mobile
   - make autofocus work on quiz
   - remove "[enter]" from start button
+  - on-screen keyboard, like wordle
   - make it all on one line 
     - make the font smaller or the div wider
-  - put a 'submit' button in
+  - put a 'submit' button in (or auto-submit?)
   - add a range slider for easier input?
-- make text inputs big enough for MAX_DIGITS_PROBLEMS and MAX_DIGITS_BITS
-- show a message on submit
+
+# Features
+- keyboard shortcuts
+  - ctrl-c to go back to menu
+- specify what you already know, then prove it (modular learning)
+- save progress
+  - local storage
+  - login
+- timed
+- keyboard shortcuts with help overlay
+- leaderboard
 - show warning when specifying invalid number of bits or problems
-- add contact info
-- add 'about'
-- add mailing list
-  - prompt at the end of a quiz to sign up for it
 - uncomment PDF part
 - add PDF export in pure front end
-- add animations
-  - 'nuh-uh' shake for wrong answers
-  - nice reward animations for right answers
-  - make the placeholders become real text for a split second before starting
-  - super mario land [pixellation animation](http://blog.swishscripts.com/2019/06/19/snes-mosaic-effect/) ("mosaic")
-- add user accounts using Userbase
-  - required for higher numbers
-  - required for PDF output?
-  - required after X uses?
+- cheat/human detection