Optimizations and debug options

internal/hero/hero.go

@@ -137,6 +137,9 @@ func New(cfg Config) *Hero {
 }
 
 func (h *Hero) Update(input Input, dt float64, bounds Bounds) {
+	if dt > 0.1 {
+		dt = 0.1
+	}
 	h.updateMovement(input, dt, bounds)
 	h.updateStamina(input, dt)
 	h.updateAnimation(dt)
@@ -145,27 +148,30 @@ func (h *Hero) Update(input Input, dt float64, bounds Bounds) {
 // Movement and physics
 
 func (h *Hero) updateMovement(input Input, dt float64, bounds Bounds) {
+	// apply gravity
 	h.VelocityY += config.Gravity * dt
 	if h.VelocityY > config.MaxFallSpeed {
 		h.VelocityY = config.MaxFallSpeed
 	}
 
-	h.Y += h.VelocityY * dt
+	newY := h.Y + h.VelocityY*dt
 
-	footPosition := h.Y
-	if footPosition >= bounds.Ground {
+	wasGrounded := h.isGrounded
+	if newY >= bounds.Ground {
 		h.Y = bounds.Ground
 		h.VelocityY = 0
 		h.isGrounded = true
 	} else {
+		h.Y = newY
 		h.isGrounded = false
 	}
 
-	if input.Jump && h.isGrounded {
+	if input.Jump && (h.isGrounded || (!wasGrounded && h.isGrounded)) {
 		h.VelocityY = config.JumpStrength
 		h.isGrounded = false
 	}
 
+	// horizontal input
 	targetVelocityX := 0.0
 	if input.Left {
 		targetVelocityX -= h.Speed
@@ -178,6 +184,7 @@ func (h *Hero) updateMovement(input Input, dt float64, bounds Bounds) {
 
 	h.isMoving = targetVelocityX != 0
 
+	// sprinting
 	h.isSprinting = input.Sprint && h.canSprint && h.Stamina > 0 && h.isMoving
 	if h.isSprinting {
 		targetVelocityX *= config.SprintSpeedMultiplier
@@ -188,17 +195,22 @@ func (h *Hero) updateMovement(input Input, dt float64, bounds Bounds) {
 		friction = config.AirFriction
 	}
 
-	h.VelocityX = h.VelocityX*friction + targetVelocityX*(1-friction)
+	frictionFactor := 1.0 - (1.0-friction)*dt*60.0
+	if frictionFactor < 0 {
+		frictionFactor = 0
+	}
+	h.VelocityX = h.VelocityX*frictionFactor + targetVelocityX*(1.0-frictionFactor)
 
-	h.X += h.VelocityX * dt
+	newX := h.X + h.VelocityX*dt
 
-	if h.X < h.Radius {
+	if newX < h.Radius {
 		h.X = h.Radius
 		h.VelocityX = 0
-	}
-	if h.X > bounds.Width-h.Radius {
+	} else if newX > bounds.Width-h.Radius {
 		h.X = bounds.Width - h.Radius
 		h.VelocityX = 0
+	} else {
+		h.X = newX
 	}
 }
 
@@ -234,12 +246,14 @@ func (h *Hero) updateAnimation(dt float64) {
 		key.state = animMove
 	}
 
+	// reset animation on state change
 	if key != h.lastAnimKey {
 		h.animFrame = 0
 		h.animTimer = 0
 		h.lastAnimKey = key
 	}
 
+	// advance animation only when moving
 	if isMoving {
 		animSpeed := config.NormalAnimSpeed * 0.5
 		if h.isSprinting {
@@ -248,12 +262,17 @@ func (h *Hero) updateAnimation(dt float64) {
 		if !h.isGrounded {
 			animSpeed = config.JumpingAnimSpeed * 0.5
 		}
+
 		h.animTimer += dt
-		frameAdvance := int(h.animTimer / animSpeed)
-		if frameAdvance > 0 {
+
+		// precise frame advancement
+		if h.animTimer >= animSpeed {
+			frameAdvance := int(h.animTimer / animSpeed)
 			h.animTimer -= animSpeed * float64(frameAdvance)
 			h.animFrame = (h.animFrame + frameAdvance) % config.AnimFrameWrap
 		}
+	} else {
+		h.animTimer = 0
 	}
 }
 
@@ -280,18 +299,28 @@ func (h *Hero) Draw(screen *ebiten.Image) {
 		actualWidth := float64(bounds.Dx())
 
 		op := &ebiten.DrawImageOptions{}
+
+		// center sprite horizontally, align bottom to feet
 		op.GeoM.Translate(-actualWidth/2, -actualHeight)
 		op.GeoM.Scale(config.HeroSpriteScale, config.HeroSpriteScale)
-		op.GeoM.Translate(h.X, h.Y)
 
+		// round position to nearest pixel for crisp rendering
+		drawX := float64(int(h.X + 0.5))
+		drawY := float64(int(h.Y + 0.5))
+		op.GeoM.Translate(drawX, drawY)
+
+		// apply visual state coloring
 		state := h.getVisualState()
 		switch state {
 		case StateExhausted:
 			op.ColorScale.ScaleWithColor(color.RGBA{R: 255, G: 100, B: 100, A: 255})
 		case StateSprinting:
+			// no color modification for sprinting
 		case StateIdle:
+			// no color modification for idle
 		}
 
+		op.Filter = ebiten.FilterNearest
 		screen.DrawImage(sprite, op)
 	}
 }