Some of you might get a kick out of this. After watching Bret Victor's talk I spent a few hours writing an "instant" version of Codea inside Codea. Basically it gives you a keyboard and you can write Codea code, any code you write is instantly run and drawn behind your code.

It's pretty interesting. Here's the code and a screenshot.

Main file is Here: http://pastebin.com/8enSYdgZ — does not paste into forums due to Emoji.

Buffer

Buffer = class()

function Buffer:init()
    self.buffer = {}
    
    self.font = "Inconsolata"
    self.fontSize = 20
    
    -- x = line, y = pos
    self.cursor = vec2(1,1)
    
    self.t = 0
    self.cursorBlink = 0
end

function Buffer:setStyle()
    textMode(CORNER)
    font( self.font )
    fill(255)
    fontSize( self.fontSize )
    textWrapWidth(10000)
end

function Buffer:cursorToScreen(c)
    -- Get a subset of the buffer
    local lines = table_slice( self.buffer, 1, c.x )
    local l = self.buffer[c.x]
    
    local upToStr = self:bufferToString(lines)
    local lstr = nil
    
    if l then
        lstr = table.concat(l)
    end
    
    pushStyle()
    
    self:setStyle()
    
    local lw = 0
    local _,lh = textSize("A")
    local emptyLine = true
    
    if lstr and lstr ~= "" then
        lw,lh = textSize(string.sub(lstr,1,c.y - 1))
        emptyLine = false
    end
    
    local pw,ph = textSize(upToStr)
    
    if emptyLine then
        ph = ph + lh
    end
    
    popStyle()
    
    return lw,(ph - lh/2)
end

function Buffer:bufferToString(b)
    local bstrings = {}
    for k,v in pairs(b) do
        table.insert(bstrings, table.concat( b[k] ) )
    end
    
    return table.concat( bstrings, "\n" )
end

function Buffer:moveCursor(o)
    self.cursor = self.cursor + o
    
    self.cursor.x = math.max(1, math.min(self.cursor.x, #self.buffer))
    
    local l = self.buffer[self.cursor.x]
    local y = self.cursor.y
    
    y = math.max(1, math.min(y, #l + 1))
    self.cursor.y = y
end

function Buffer:insertCharacter(c)
    local l = self.buffer[self.cursor.x]
    
    if l == nil then
        l = {}
        self.buffer[self.cursor.x] = l
    end

    if c == "\n" then
        local start = table_slice(l,1,self.cursor.y)
        local tail = table_slice(l,self.cursor.y+1,#l)
        
        table[self.cursor.x] = start
        table.insert(self.buffer, self.cursor.x+1, tail)
        
        self.cursor = vec2( self.cursor.x + 1, 1 )
    elseif c == BACKSPACE then
        if self.cursor.y == 1 then
            -- delete line
            local prevLine = self.buffer[self.cursor.x - 1]
            
            table.remove(self.buffer, self.cursor.x)
            
            if prevLine then
                self.cursor = vec2(self.cursor.x - 1, #prevLine + 1)
                table_append( prevLine, l )
            end
        else
            -- delete character
            table.remove(l, self.cursor.y - 1 )
            self.cursor = vec2(self.cursor.x, self.cursor.y - 1 )
        end
    else
        table.insert(l, self.cursor.y, c)
    
        self.cursor = vec2( self.cursor.x, self.cursor.y + 1 )
    end
end

function Buffer:draw()
    self.t = self.t + 8 * DeltaTime
    self.cursorBlink = (math.sin(self.t) + 1) * 128
    
    pushStyle()
    
    self:setStyle()
    
    local str = self:toString()
    local w,h = textSize(str)
    
    pushMatrix()
    translate( 40, -40 )
    
    text(str, 0, HEIGHT - h)
    
    -- Draw cursor
    -- Cursor pos x,y
    local cpx,cpy = self:cursorToScreen(self.cursor)
    fill(0, 87, 255, self.cursorBlink)
    rectMode(CENTER)
    rect(cpx,HEIGHT - cpy,5,22)
    
    popMatrix()
    popStyle()
end

function Buffer:clear()
    self.cursor = vec2(1,1)
    self.buffer = {}
end

function Buffer:toString()
    return self:bufferToString(self.buffer)
end

function Buffer:toStringWithoutActiveLine()
    local bstrings = {}
    for k,v in pairs(self.buffer) do
        if k ~= self.cursor.x then
            table.insert(bstrings, table.concat( self.buffer[k] ) )
        end
    end
    
    return table.concat( bstrings, "\n" )
end

EmButton

-- Emoji Button
EmButton = class()

function EmButton:init(pos,txt)
    -- you can accept and set parameters here
    self.pos = pos
    self.text = txt
    self.action = nil
    self.highlight = false
    self.color = color(255,255,255,255)
end

function EmButton:size()
    pushStyle()
    self:setStyle()

    local w,h = textSize(self.text)

    popStyle()

    return w,h
end

function EmButton:hitTest(lp)
    local w,h = self:size()

    local left,right = self.pos.x - w/2, self.pos.x + w/2
    local top,bottom = self.pos.y + h/2, self.pos.y - h/2

    if lp.x > left and lp.x < right and
       lp.y > bottom and lp.y < top then
        return true
    end

    return false
end

function EmButton:setStyle()
    fill(self.color)
    noStroke()
    textMode(CENTER)
    fontSize(50)
    font("AppleColorEmoji")
end

function EmButton:draw()
    pushMatrix()

    translate(self.pos.x,self.pos.y)

    pushStyle()
    self:setStyle()

    text(self.text,0,0)

    popStyle()

    popMatrix()
end

function EmButton:touched(touch)
    if touch.state == ENDED then
        -- Tapped
        if self:hitTest( vec2(touch.x,touch.y) ) then
            if self.action then self.action() end
        end
    end
end