If you're playing on a computer that doesn't have a dedicated graphics card, you may experience poor performance. To improve your performance you may try setting the game's graphics quality to "Low".
ZQD/WAD or Up/Left/Right arrow keys: Movement
S or Down arrow key: Regenerate HP
Left Mouse Button: Use Weapon
Right Mouse Button: Drop a Satchel Charge/Explode a dropped Satchel Charge