feat: add collapse animation

pkg/anim/collapse.go

@@ -0,0 +1,47 @@
+package anim
+
+import (
+	"time"
+
+	"github.com/cfoust/cy/pkg/emu"
+	"github.com/cfoust/cy/pkg/geom/image"
+)
+
+type Collapse struct {
+	last    time.Duration
+	current image.Image
+}
+
+var _ Animation = (*Collapse)(nil)
+
+func (c *Collapse) Init(start image.Image) {
+	c.current = start
+}
+
+func (c *Collapse) Update(delta time.Duration) image.Image {
+	if (delta - c.last) < (time.Second / TICKS_PER_SECOND) {
+		return c.current
+	}
+
+	c.last = delta
+
+	size := c.current.Size()
+
+	for row := size.R - 1; row >= 0; row-- {
+		for col := size.C - 1; col >= 0; col-- {
+			// can't go past bottom
+			if row+1 == size.R {
+				continue
+			}
+
+			next := c.current[row+1][col]
+			if !next.IsEmpty() {
+				continue
+			}
+			c.current[row+1][col] = c.current[row][col]
+			c.current[row][col] = emu.EmptyGlyph()
+		}
+	}
+
+	return c.current
+}

pkg/anim/module.go

@@ -70,6 +70,7 @@ func NewAnimator(
 
 func Random() Animation {
 	anims := []Animation{
+		&Collapse{},
 		&Midjo{},
 		&Cyform{},
 		&Conway{},

pkg/emu/state.go

@@ -84,6 +84,10 @@ type Glyph struct {
 	FG, BG Color
 }
 
+func (g Glyph) IsEmpty() bool {
+	return g.Char == ' '
+}
+
 func EmptyGlyph() Glyph {
 	return Glyph{
 		Char: ' ',