comparative overview
| BlC | AW | D3D | HL2 | SL | |
| in-game building | - | + | +/- | - | ++ |
| avatar manipulation | + | ++ | +/- | + | ++ |
| artifical intelligence | + | - | +/- | + | - |
| server-side scripts | + | - | +/- | + | ++ |
| client-side scripts | ++ | - | +/- | + | - |
| extensibility | + | - | ++ | + | +/- |
| open source | - | - | ++ | - | +/- |
| open standards | - | - | +/- | - | +/- |
| interaction | +/- | +/- | ++ | ++ | +/- |
| graphics quality | +/- | +/- | ++ | ++ | + |
| built-in physics | - | - | + | ++ | + |
| object collision | - | - | ++ | ++ | + |
| content tool support | +/- | - | ++ | + | - |