Make sure turbo mode is turned on or otherwise use turbowarp...
Tap the enemies to deal damage, collect coins, upgrade heroes and progress through as many zones as possible. This game has save codes, go to the settings tab in-game. (cog button)
From Level 200 (Inclusive), heroes get x4 multipliers every 25 lvls.
From Level 1000 (Inclusive), heroes get x10 instead of x4 multipliers every 1000 levels.