Scattered throughout the levels are colored crystals. Shoot blue crystals to create element shards that can be collected. Red crystals will drop health shards. Tap the shard in order to collect it. When health shards are on the ground nearby, red "+" indicators will appear next to the normal indicator buttons.
Enemy locations
There are two indicator buttons to the left and right sides that allow you to rotate and change your view. When enemies are present, the corresponding indicator will turn blue and display a number that corresponds to how many enemies there are in that direction. If they are advancing towards you, the indicated will turn yellow. When an enemy is preparing to attack, the indicator will turn red.
Hardcore and Psychotic difficulties
Earn a three star rank on a level under normal campaign difficulty to unlock the Hardcore and Psychotic difficulties for that level. The Psychotic difficulty is harder than Hardcore. The rewards in each of those difficulties will be greater than normal.
Reloading
Actively reload instead of relying on the auto reload feature. When your current clip is about to run out, an indicator will appear at the top right, along with a warning at the top of the screen. When only a few shots are remaining, the message "Ammo critical" will appear. At this point, tap the gun icon at the top right to start an active reload. When a clip completely empties, the automatic reload will start but will require more time.
Scoring
When you get a kill, your score multiplier increases by one. You will have a few seconds between each kill before the multiplier drops back to one.
Shield
Holding two fingers to activate your shield. The center of the shield will be where your two fingers are positioned. Try to keep projectiles centered to maximize the shield's effectiveness. The shield has an energy gauge that refills over time and drops each time it absorbs a projectile. The closer the projectiles are to the center of the shield, the less energy it will lose.
Crystal shards...