The hardware timings behind the calculator’s screen refreshing are a real challenge. With around 50 thousand cycles available, rendering the game background with walls and floors seems impossible. The struggle is real as we try to optimize the tile rendering process with disregard for memory and register usage. Even with clever tweaks like loop unrolling and indirect cycle reductions, we still fall short of the necessary 73,440 cycles. It’s a race against time to make this game a reality, but the determination to find a solution is what keeps the possibility of success alive.
http://masochistcoder.blogspot.com/2016/05/performance.html