'T' is for toggling
Pressing 'T' turns the sound on or off - but only while a game is in progress (see 27022).
In addition to the documented movement keys - 'Q', 'Z', 'I' and 'P' - the keys '1', '2', '3' and '4' can also be used to move Horace left, right, down and up (see 25284).
Game speed
When Horace moves from maze 4 back to maze 1, the game speed parameter at 31842 is decreased by one, which increases the speed of the game (see 27044). It reaches its lowest value (1) on the 29th maze, and then remains at that value until the game ends.
Variable fruit bonus
The bonus awarded for eating a cherry or strawberry depends on Horace's direction of approach. He scores 60 when moving up or down over the fruit (50 for the fruit itself, plus 10 for the green leaves, which count as a flower), and 100 when moving left or right over the fruit (50 for each half of the fruit).