Complete challenges, such as killing aliens or collecting coins to unlock alternate costumes.
Power-ups
Power-ups will give you a boost for a short amount of time. The jetpack it allows you to fly and shoot enemies in the air and the ones on the ground. The magnet pulls coins closer to you. You can use the coins that you have collected to upgrade weapons and power-ups.
Time Clocks
Collect the time clocks at every opportunity to extend the timer. If the timer runs out, aliens will snatch you and the game ends.