Quick little project to show and explain the difference between "when key pressed" and "key pressed?" blocks. Right arrow controls Sprite1 (Giga), left arrow controls Sprite2 (Pico). Notice the difference in behaviour - in particular, the way Giga pauses just after each time you press the right arrow key.
Try changing your keyboard settings (in System Prefs, or Control Panels) and see what difference it makes to the way Giga moves. This demonstrates why it's generally better to use the blue sensor blocks for smooth movement, rather than the "when key pressed" hat blocks. (Though "see inside" for a way to use "when key pressed" to get smooth movement.)
