The framerate is very, very jittery. This makes it hard to even control the panel right. One moment the ball comes flying in fast, then it stops due to a harsh drop in framerate, but I am moving my mouse along with the ball - or so I think - but it "tricks" me and I drop it.

I am on Windows 10 and found the framerate not to be constant at all. The ball does not move smoothly.

I find it irritating that I have the mouse cursor visible when it is inside the window. I think you want to hide it.

One thing I want to point out which is great is that you track the mouse position outside the window. This game would not be playable otherwise, so good job!

Thank you for using Ebiten! I tested this but found a crash:

$ go run .
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x4150f4e]

goroutine 5 [running]:
github.com/hajimehoshi/ebiten.(*Image).isDisposed(...)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/image.go:57
github.com/hajimehoshi/ebiten.(*Image).Bounds(...)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/image.go:375
github.com/hajimehoshi/ebiten.(*Image).Size(...)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/image.go:52
arkanoid/systems/sprite.drawImageWithWrap(0xc000024580, 0xc00000e3e0)
        /Users/hajimehoshi/ebiten-games/arkanoid-go/systems/sprite/render.go:51 +0x6e
arkanoid/systems/sprite.RenderSystem(0xc00006c360, 0xc000012a50, 0xc000010088, 0xc000024580)
        /Users/hajimehoshi/ebiten-games/arkanoid-go/systems/sprite/render.go:42 +0x2a8
main.game.Update(0xc00006c360, 0xc000012a50, 0xc000010088, 0xc000024580, 0x20, 0x30)
        /Users/hajimehoshi/ebiten-games/arkanoid-go/main.go:36 +0x95
github.com/hajimehoshi/ebiten.(*imageDumper).update(0xc000254080, 0xc000024580, 0x0, 0x0)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/imagedumper_desktop.go:106 +0x4e
github.com/hajimehoshi/ebiten.(*imageDumperGame).Update(0xc00000e500, 0xc000024580, 0x468a960, 0x0)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/run.go:180 +0x44
github.com/hajimehoshi/ebiten.(*uiContext).update(0x466cb40, 0xc0001d6140, 0x0, 0x0)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/uicontext.go:262 +0x150
github.com/hajimehoshi/ebiten.(*uiContext).Update(0x466cb40, 0xc0001d6140, 0x0, 0x0)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/uicontext.go:239 +0xb4
github.com/hajimehoshi/ebiten/internal/uidriver/glfw.(*UserInterface).update(0x4667f20, 0x441a0a0, 0x466cb40, 0xc0001d0001, 0xc000048668)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/internal/uidriver/glfw/ui.go:751 +0x1d9
github.com/hajimehoshi/ebiten/internal/uidriver/glfw.(*UserInterface).loop(0x4667f20, 0x441a0a0, 0x466cb40, 0x0, 0x0)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/internal/uidriver/glfw/ui.go:797 +0xec
github.com/hajimehoshi/ebiten/internal/uidriver/glfw.(*UserInterface).run(0x4667f20, 0x441a0a0, 0x466cb40, 0x0, 0x0)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/internal/uidriver/glfw/ui.go:669 +0x232
github.com/hajimehoshi/ebiten/internal/uidriver/glfw.(*UserInterface).Run.func1(0xc000012ac0, 0xc00006c3c0, 0x4667f20, 0x441a0a0, 0x466cb40)
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/internal/uidriver/glfw/ui.go:535 +0xbc
created by github.com/hajimehoshi/ebiten/internal/uidriver/glfw.(*UserInterface).Run
        /Users/hajimehoshi/go/pkg/mod/github.com/hajimehoshi/[email protected]/internal/uidriver/glfw/ui.go:532 +0x154
exit status 2

In the main menu I can press UP/DOWN but only half of the time will this change the option. Are you not reacting to key events but instead rely on the key state during the frame?

I find that depending on how the ball bounces off blocks it flies nearly horizontally sometimes. This means it takes ages to come back down to the bottom. You should probably have some margin of vertical movement always. It seems to me that it would be possible that we have a perfectly horizontal ball that never does anything anymore after deleting its line of blocks. This might lead to an infinite game.