The keys:

• Left: Move left
• Right: Move right
• Ctrl or Space: Fire
• Alt or C: Button 2
• 1: 1 Player start
• 2: 2 Players start
• 3: Insert coin (slot 1)
• 4: Insert coin (slot 2)
• 5: Insert coin (slot 3)
• Keypad +: Increase frame skipping rate
• Keypad -: Decrease frame skipping rate