V0.10.3 - Antigravity zones and performance upgrades

Changes in V0.10.3:

• Added particles for lasers, shrink and growth rays 
• Reduced the number of screws on the levels, instead they're spawning more frequently
• Changed how screw magnet works to increase performance
• You can now activate the power-ups by pressing S, F and Space on your keyboard (these bindings are displayed in the settings and the shop)
• Changed how the shield power-up recharges in endless and campaign modes, now it counts the distance you have travelled, and not the distance from the start of the level
• The shield power-up lasts half as long
• The timer won't be displayed if you fail the level
• Added levels 11 - 15
• Added antigravity zones
• Added 4 new endless sections with the new antigravity zones