Added a label when player gets sparks.
Improved labels when player gets a spark.

Multi label now displays current multiplier.
Spark label now has a spark icon for clarity.
Multiplier below player option is now turned off by default.
Changed volume controls to be slider instead of on/off.

Save the volume values now instead of on/of in player data.

Disabled mute and fullscreen hotkeys. Removed UI from game.
After beating a world, now moves directly to the next world.
Created and hooked up better tutorial which triggers on Hive 1-1.

Minor tweaks to first few levels to make them not so boring to restart if
you die.
Tweaks to early levels to make them less boring at the start. Basically
increased initial spawns.

Ensured that when you impulse two tanks that are touching, they both die,
by adding a grace period.

After completing ult tutorial, now goes directly to world 2.

Trolls are now slightly harder to kill. Even when you impulse them when
they're inactive, you at least have to think about the direction.

Fixed a bug where first_time wasn't being set in impulse_game_state, which
was causing various issues like boss text never showing up.