I've just released an update with lots of new content and features!

Full changelog:

• New game modes!
  • "Battle" mode for multiplayer games
    • In this mode you compete to finish 30 lines first, and completing two or more lines at once sends garbage to your opponent
      
  • "25 Lines" mode for singleplayer games
    • The goal of this mode is to complete 25 lines.
• Added support for gamepads!
  • Button mappings can be found in the controls menu
• Music has been added to the game!
  • There are three tracks to choose from, but you can also play without music
• New game options screens
  • This is where you select the game mode you want to play and you can also select the level to start at, the height of garbage (for game modes that support it), and the music track to listen to
• New sound effects for winning and losing games!
• Blocks now start at the very top of the screen
• There is no longer a cap on the level you can reach (previously topped out at level 20)
• The soft drop speed has been tweaked to be slightly faster
• The game now pauses when it loses focus
• There are now short input delays on pausing and game end to prevent unintentionally restarting the game or unpausing
• The version number now shows up on the title screen