#define COORD(x) ((x) * TILESIZE + BORDER)
#define FROMCOORD(x) (((x) - BORDER) / TILESIZE)
-static char *interpret_move(game_state *state, game_ui *ui, game_drawstate *ds,
+static char *interpret_move(game_state *state, game_ui *ui, const game_drawstate *ds,
int x, int y, int button)
{
enum {none, forwards, backwards, hint};