Arrow keys move the tape -- i.e. ← will move the head from position 0 to 1. Green cells are "virtual", meaning they have no value in the backing data structure and are thus assigned a value of 0.
Note: this is probably not that interesting on a mobile device...
The following is the instruction set for a 3-state, 2-symbol Busy Beaver. A type of program that terminates in the most number of steps given the number of states & inputs. The active instruction is highlighted in green.
| A | 0 | P1 | R | B |
| A | 1 | P1 | R | H |
| B | 0 | P0 | R | C |
| B | 1 | P1 | R | B |
| C | 0 | P1 | L | C |
| C | 1 | P1 | L | A |