Level Collision and Scrolling Fixes

* Fix the level collision bug that allowed clipping thru a ceiling while
  climbing up a wall.
* Fix the scrolling behavior to keep the character on-screen no matter
  how fast the character is moving, especially downwards.
* Increase player speed and gravity.
* New cheat: "ghost mode" disables clipping for the player character.
* Mark an actor as "grounded" if they fall and are stopped by the lower
  level border, so they may jump again.

docs/Shell.md

@@ -9,6 +9,7 @@
 * `import antigravity` - during Play Mode, disables gravity for the player
   character and allows free movement in all directions with the arrow keys.
   Enter the cheat again to restore gravity to normal.
+* `ghost mode` - during Play Mode, toggles noclip for the player character.
 
 ## Bool Props
 

pkg/balance/numbers.go

@@ -12,12 +12,11 @@ var (
 	// Window scrolling behavior in Play Mode.
 	ScrollboxHoz  = 256 // horizontal px from window border to start scrol
 	ScrollboxVert = 128
-	ScrollMaxVelocity = 8 // 24
 
 	// Player speeds
-	PlayerMaxVelocity  = 8
+	PlayerMaxVelocity  = 10
 	PlayerAcceleration = 2
-	Gravity            = 2
+	Gravity            = 6
 
 	// Default chunk size for canvases.
 	ChunkSize = 128

pkg/collision/collide_level.go

@@ -84,7 +84,8 @@ func CollidesWithGrid(d doodads.Actor, grid *level.Chunker, target render.Point)
 			d.SetGrounded(false)
 		}
 		if result.Top {
-			// Never seen it touch the top.
+			ceiling = true
+			P.Y++
 		}
 		if result.Left {
 			P.X++
@@ -141,6 +142,13 @@ func CollidesWithGrid(d doodads.Actor, grid *level.Chunker, target render.Point)
 	result.Reset()
 	result.MoveTo = P
 	for point := range render.IterLine(P, target) {
+		// Before we compute their next move, if we're already capping their
+		// height make sure the new point stays capped too. This prevents them
+		// clipping thru a ceiling if they were also holding right/left too.
+		if capHeight != 0 && point.Y < capHeight {
+			point.Y = capHeight
+		}
+
 		if has := result.ScanBoundingBox(render.Rect{
 			X: point.X,
 			Y: point.Y,
@@ -174,7 +182,6 @@ func CollidesWithGrid(d doodads.Actor, grid *level.Chunker, target render.Point)
 		// So far so good, keep following the MoveTo to
 		// the last good point before a collision.
 		result.MoveTo = point
-
 	}
 
 	// If they hit the roof, cap them to the roof.
@@ -225,10 +232,11 @@ func (c *Collide) ScanBoundingBox(box render.Rect, grid *level.Chunker) bool {
 	var wg sync.WaitGroup
 	for _, job := range jobs {
 		wg.Add(1)
-		go func(job jobSide) {
+		job := job
+		go func() {
 			defer wg.Done()
 			c.ScanGridLine(job.p1, job.p2, grid, job.side)
-		}(job)
+		}()
 	}
 
 	wg.Wait()
@@ -239,6 +247,15 @@ func (c *Collide) ScanBoundingBox(box render.Rect, grid *level.Chunker) bool {
 // for any pixels to be set, implying a collision between level geometry and the
 // bounding boxes of the doodad.
 func (c *Collide) ScanGridLine(p1, p2 render.Point, grid *level.Chunker, side Side) {
+	// If scanning the top or bottom line, offset the X coordinate by 1 pixel.
+	// This is because the 4 corners of the bounding box share their corner
+	// pixel with each side, so the Left and Right edges will check the
+	// left- and right-most point.
+	if side == Top || side == Bottom {
+		p1.X += 1
+		p2.X -= 1
+	}
+
 	for point := range render.IterLine(p1, p2) {
 		if swatch, err := grid.Get(point); err == nil {
 			// We're intersecting a pixel! If it's a solid one we'll return it

pkg/commands.go

@@ -63,6 +63,23 @@ func (c Command) Run(d *Doodle) error {
 			d.Flash("Use this cheat in Play Mode to disable gravity for the player character.")
 		}
 		return nil
+	} else if c.Raw == "ghost mode" {
+		if playScene, ok := d.Scene.(*PlayScene); ok {
+			playScene.noclip = !playScene.noclip
+			playScene.Player.SetNoclip(playScene.noclip)
+
+			playScene.antigravity = playScene.noclip
+			playScene.Player.SetGravity(!playScene.antigravity)
+
+			if playScene.noclip {
+				d.Flash("Clipping disabled for player character.")
+			} else {
+				d.Flash("Clipping and gravity restored for player character.")
+			}
+		} else {
+			d.Flash("Use this cheat in Play Mode to disable clipping for the player character.")
+		}
+		return nil
 	}
 
 	switch c.Command {

pkg/play_scene.go

@@ -51,6 +51,7 @@ type PlayScene struct {
 	// Player character
 	Player            *uix.Actor
 	antigravity       bool // Cheat: disable player gravity
+	noclip            bool // Cheat: disable player clipping
 	playerJumpCounter int  // limit jump length
 }
 
@@ -438,7 +439,7 @@ func (s *PlayScene) movePlayer(ev *event.State) {
 		velocity.Y = -playerSpeed
 
 		if s.Player.Grounded() {
-			s.playerJumpCounter = 20
+			s.playerJumpCounter = 12
 		}
 	}
 	if ev.Down && s.antigravity {

pkg/uix/actor.go

@@ -31,6 +31,7 @@ type Actor struct {
 	// Actor runtime variables.
 	hasGravity bool
 	isMobile   bool // Mobile character, such as the player or an enemy
+	noclip     bool // Disable collision detection
 	hitbox     render.Rect
 	data       map[string]string
 
@@ -89,6 +90,12 @@ func (a *Actor) IsMobile() bool {
 	return a.isMobile
 }
 
+// SetNoclip sets the noclip setting for an actor. If true, the actor can
+// clip through level geometry.
+func (a *Actor) SetNoclip(v bool) {
+	a.noclip = v
+}
+
 // GetBoundingRect gets the bounding box of the actor's doodad.
 func (a *Actor) GetBoundingRect() render.Rect {
 	return doodads.GetBoundingRect(a)

pkg/uix/actor_collision.go

@@ -63,7 +63,7 @@ func (w *Canvas) loopActorCollision() error {
 
 			// Get the actor's velocity to see if it's moving this tick.
 			v := a.Velocity()
-			if a.hasGravity {
+			if a.hasGravity && v.Y >= 0 {
 				v.Y += balance.Gravity
 			}
 
@@ -86,7 +86,11 @@ func (w *Canvas) loopActorCollision() error {
 					w.OnLevelCollision(a, info)
 				}
 			}
-			delta = info.MoveTo // Move us back where the collision check put us
+
+			// Move us back where the collision check put us
+			if !a.noclip {
+				delta = info.MoveTo
+			}
 
 			// Move the actor's World Position to the new location.
 			a.MoveTo(delta)
@@ -121,7 +125,6 @@ func (w *Canvas) loopActorCollision() error {
 					W: boxes[tuple.B].W,
 					H: boxes[tuple.B].H,
 				}
-				// lastGoodBox = originalPositions[b.ID()] // boxes[tuple.B] // worst case scenario we get blocked right away
 			)
 
 			// Firstly we want to make sure B isn't able to clip through A's
@@ -206,7 +209,9 @@ func (w *Canvas) loopActorCollision() error {
 					}
 				}
 
+				if !b.noclip {
 					b.MoveTo(lastGoodBox.Point())
+				}
 			} else {
 				log.Error(
 					"ERROR: Actors %s and %s overlap and the script returned false,"+

pkg/uix/canvas_scrolling.go

@@ -126,14 +126,11 @@ func (w *Canvas) loopFollowActor(ev *event.State) error {
 		)
 
 		// Scroll left
-		if APosition.X-VP.X <= balance.ScrollboxHoz {
-			var delta = APosition.X - VP.X
-			if delta > balance.ScrollMaxVelocity {
-				delta = balance.ScrollMaxVelocity
-			}
+		if APosition.X <= VP.X+balance.ScrollboxHoz {
+			var delta = VP.X + balance.ScrollboxHoz - APosition.X
 
-			if delta < 0 {
 			// constrain in case they're FAR OFF SCREEN so we don't flip back around
+			if delta < 0 {
 				delta = -delta
 			}
 			scrollBy.X = delta
@@ -141,22 +138,13 @@ func (w *Canvas) loopFollowActor(ev *event.State) error {
 
 		// Scroll right
 		if APosition.X >= VP.W-ASize.W-balance.ScrollboxHoz {
-			var delta = VP.W - ASize.W - balance.ScrollboxHoz
-			if delta > balance.ScrollMaxVelocity {
-				delta = balance.ScrollMaxVelocity
-			}
-			scrollBy.X = -delta
+			var delta = VP.W - ASize.W - APosition.X - balance.ScrollboxHoz
+			scrollBy.X = delta
 		}
 
 		// Scroll up
-		if APosition.Y-VP.Y <= balance.ScrollboxVert {
-			var delta = APosition.Y - VP.Y
-			if delta > balance.ScrollMaxVelocity {
-				delta = balance.ScrollMaxVelocity
-			}
-
-			// TODO: add gravity to counteract jitters on scrolling vertically
-			scrollBy.Y -= balance.Gravity
+		if APosition.Y <= VP.Y+balance.ScrollboxVert {
+			var delta = VP.Y + balance.ScrollboxVert - APosition.Y
 
 			if delta < 0 {
 				delta = -delta
@@ -166,14 +154,13 @@ func (w *Canvas) loopFollowActor(ev *event.State) error {
 
 		// Scroll down
 		if APosition.Y >= VP.H-ASize.H-balance.ScrollboxVert {
-			var delta = VP.H - ASize.H - balance.ScrollboxVert
-			if delta > balance.ScrollMaxVelocity {
-				delta = balance.ScrollMaxVelocity
+			var delta = VP.H - ASize.H - APosition.Y - balance.ScrollboxVert
+			if delta > 300 {
+				delta = 300
+			} else if delta < -300 {
+				delta = -300
 			}
-			scrollBy.Y = -delta
-
-			// TODO: add gravity to counteract jitters on scrolling vertically
-			scrollBy.Y += balance.Gravity * 3
+			scrollBy.Y = delta
 		}
 
 		if scrollBy != render.Origin {

pkg/uix/canvas_wallpaper.go

@@ -57,6 +57,9 @@ func (w *Canvas) loopContainActorsInsideLevel(a *Actor) {
 			if int64(orig.Y+size.H) > w.wallpaper.maxHeight {
 				var delta = w.wallpaper.maxHeight - int64(orig.Y+size.H)
 				moveBy.Y = int(delta)
+
+				// Allow them to jump from the bottom by marking them as grounded.
+				a.SetGrounded(true)
 			}
 		}
 	}