Finished homework and optional challenge

src/Main.elm

@@ -2,6 +2,7 @@ module Main exposing (..)
 
 import Asteroids
 import Mario
+import TimeTravel exposing (addTimeTravel)
 
 import Playground
 
@@ -14,4 +15,5 @@ gameApplication game =
 -- The main entry point for the app
 
 main = Mario.game
+  |> addTimeTravel
   |> gameApplication

src/Mario.elm

@@ -49,6 +49,9 @@ view computer mario =
     [ rectangle (rgb 174 238 238) w h  -- sky
     , rectangle (rgb 74 163 41) w 100  -- ground
         |> moveY b
+    , rectangle (rgb 245 97 11) 100 100 -- lava
+        |> moveY b
+        |> moveX 200
     , mario.trace
         |> pathToPolygonVertices 1.5
         |> polygon black
@@ -98,9 +101,21 @@ update computer mario =
     newY = max 0 (mario.y + dt * vy)
   in
     { mario
-      | x = newX
-      , y = newY
-      , vx = vx
+      | x = 
+          if touchingLava newX newY then
+            0
+          else 
+            newX
+      , y = 
+          if touchingLava newX newY then
+            0
+          else 
+            newY
+      , vx = 
+          if touchingLava newX newY then
+            0
+          else 
+            vx
       , vy = (newY - mario.y) / dt
       , dir =
           if (toX computer.keyboard) < 0 then
@@ -109,7 +124,11 @@ update computer mario =
             Right
           else
             mario.dir  -- face direction of last movement when standing still
-      , trace = addPointUnlessDuplicate (newX, newY) mario.trace
+      , trace = 
+          if touchingLava newX newY then
+            []
+          else 
+            addPointUnlessDuplicate (newX, newY) mario.trace
     }
 
 addPointUnlessDuplicate point path =
@@ -118,6 +137,20 @@ addPointUnlessDuplicate point path =
   else
     point :: path
 
+
+touchingLava x y =
+  if x < 250 then
+    if x > 150 then 
+      if y == 0 then
+        True
+      else
+        False
+    else 
+      False
+  else 
+    False
+
+
 -- HELPERS
 
 -- Elm’s playground package doesn't have any way to stroke a path.

src/TimeTravel.elm

@@ -3,3 +3,91 @@ module TimeTravel exposing (addTimeTravel)
 import Playground exposing (..)
 import Set
 
+controlBarHeight = 64
+maxVisibleHistory = 2000
+
+-- Converts an index in the history list to an x coordinate on the screen
+historyIndexToX computer index =
+  (toFloat index) / maxVisibleHistory * computer.screen.width
+
+addTimeTravel rawGame =
+  { initialState = initialStateWithTimeTravel rawGame
+  , updateState = updateWithTimeTravel rawGame
+  , view = viewWithTimeTravel rawGame
+  }
+
+initialStateWithTimeTravel rawGame =
+  {rawModel = rawGame.initialState 
+  , paused = False
+  , history = []
+  , historyPlaybackPosition = 0}
+
+viewWithTimeTravel rawGame computer model =
+  let
+    -- Creates a rectangle at the top of the screen, stretching from the
+    -- left edge up to a specific position within the history timeline
+    historyBar color opacity index =
+      let
+        width = historyIndexToX computer index
+      in
+        rectangle color width controlBarHeight  
+          |> move (computer.screen.left + width / 2)
+                  (computer.screen.top - controlBarHeight / 2)
+          |> fade opacity
+    helpMessage =
+        if model.paused then
+          "Press R to resume"
+        else
+          "Press T to time travel"
+  in
+    (rawGame.view computer model.rawModel) ++
+      [ historyBar black 0.3 maxVisibleHistory
+      , historyBar red 0.6 (List.length model.history) -- idk why this won't work?
+      , historyBar purple 0.6 model.historyPlaybackPosition
+      , words white helpMessage
+        |> move 0 (computer.screen.top - controlBarHeight / 2)
+      ]
+
+
+updateWithTimeTravel rawGame computer model =
+  if (keyPressed "T" computer) && (computer.mouse.down)then 
+    let
+      newPlaybackPosition = min (mousePosToHistoryIndex computer) (List.length model.history)
+      replayHistory pastInputs = List.foldl rawGame.updateState rawGame.initialState pastInputs
+    in
+      { model
+        | historyPlaybackPosition = newPlaybackPosition
+        , rawModel = replayHistory (List.take newPlaybackPosition model.history)
+      }
+  else if keyPressed "T" computer then 
+    {model | paused = True}
+  else if keyPressed "R" computer then  
+    {model 
+      | paused = False
+      , history = List.take model.historyPlaybackPosition model.history
+    }
+  else if keyPressed "C" computer then
+    {model 
+      | history = []
+      , rawModel = List.foldl rawGame.updateState rawGame.initialState model.history
+      }
+  else if model.paused then
+    model
+  else 
+    { model | rawModel = rawGame.updateState computer model.rawModel
+    , history = model.history ++ [computer] 
+    , historyPlaybackPosition = List.length model.history + 1}
+
+
+keyPressed keyName computer =
+  [ String.toLower keyName
+  , String.toUpper keyName
+  ]
+    |> List.any (\key -> Set.member key computer.keyboard.keys)
+
+
+-- Converts the mouse's current position to an index within the history list
+mousePosToHistoryIndex computer =
+  (computer.mouse.x - computer.screen.left)
+    / computer.screen.width * maxVisibleHistory
+  |> round