visible is not a member of "panel"
Also mein Script seiht so aus:

PANEL* main_pan =
{
bmap = "main.pcx";
pos_x = 0;
pos_y = 0;
button (75,150,"button_play.pcx", "button_play.pcx", "button_play.pcx", play_program, NULL, NULL);
flags = OVERLAY | VISIBLE;
}

function play_program()
{
while (key_any) {wait (1);}
main_pan.visible = off;
fps_max = 140;
level_load("roller.wmb"); // load the level
wait (2); // wait until the level is loaded
}
Müsste doch stimmen?
Und bei dem lite-c script kommt: show is not declariert