Controls
The default keyboard layout is the following. Left: A Right: D Forward: W Backward: S

Action: Left mouse button
Use: Right mouse button
Toggle firs person view : C
Suicide: K

Pause: Pause
Menu: Esc
Screenshot: F9
Press the [Action] button to perform the special function of the selected ball.

Ball type | Action
Crystal | Sparkling.
Bubble | Jump. Hold to glide.
Iron | Slowdown.
Sonic | Use nitro.
Evacuation | Jump.

The function of the [Use] button varies according to different situations.
The current function is displayed in the top right corner of the screen.
The most common situations that you may face:

Near a question mark: | Read hints.
Near a Balltar: | Aquire a new ball type.
Near a Tiny on the HUB: | Talk to the Tiny.
On a pavement: | Enter a level.
Near a ball or capsule containing a Tiny: | Get attached to the selected object.