design.v

module game(    
    input CLK, 
    
    output LED_R0, 
    output LED_R1, 
    output LED_R2, 
    output LED_R3, 
    output LED_R4, 
    output LED_R5, 
    output LED_R6, 
    output LED_R7,

    output LED_C0, 
    output LED_C1, 
    output LED_C2, 
    output LED_C3,
    
    input BTN_1,
    input BTN_2,
    input BTN_RST
    );
    
    reg STOP;
    reg [22:0] TICK_COUNTER = 0;

    reg [11:0] COUNTER = 0;
    reg [7:0]  LED_R; 
    reg [3:0]  LED_C;
    reg [7:0]  LED_MATRIX [3:0];

    reg [3:0] RESYNC_BTN1;
    reg [3:0] RESYNC_BTN2;
    reg [3:0] RESYNC_BTN_RST;

    reg [7:0] BUCKET_POSITION;
    reg [2:0] EGG_POSITION_X;
    reg [1:0] EGG_POSITION_Y;

    reg [63:0] RND;

    always@(posedge CLK) begin
        if(STOP) begin
            RESYNC_BTN1 <= {RESYNC_BTN1[2:0], BTN_1 == 0};
            RESYNC_BTN2 <= {RESYNC_BTN2[2:0], BTN_2 == 0};  

            // If the move right button is pressed move bucket to the right
            if(~RESYNC_BTN1[3] & RESYNC_BTN1[2]) begin
                if(BUCKET_POSITION != 7) begin
                    LED_MATRIX[3] <= LED_MATRIX[3] >> 1;
                    BUCKET_POSITION <=  BUCKET_POSITION + 1;
                end
            end

            // If the move left button is pressed move bucket to the left
            if(~RESYNC_BTN2[3] & RESYNC_BTN2[2]) begin
                if(BUCKET_POSITION != 1) begin
                    LED_MATRIX[3] <= LED_MATRIX[3] << 1;
                    BUCKET_POSITION <= BUCKET_POSITION - 1;
                end
            end

            // Generate egg and drop straight down as per the laws of physics :-)
            if(TICK_COUNTER == 0) begin
                LED_MATRIX[0] <= 0;
                LED_MATRIX[1] <= 0;
                LED_MATRIX[2] <= 0;

                if(EGG_POSITION_Y == 0) begin 
					EGG_POSITION_X = RND[2: 0];
					RND = (RND >> 1) ^ RND;
                end

                if(EGG_POSITION_Y != 3)
                    LED_MATRIX[EGG_POSITION_Y] <= 1 << EGG_POSITION_X;

                EGG_POSITION_Y <= EGG_POSITION_Y + 1;
            end

            // Check if the egg has been caught in the basket
            if(TICK_COUNTER == 0 && EGG_POSITION_Y == 3) begin
                if(!(LED_MATRIX[3] & (1 << EGG_POSITION_X)))
                    STOP <= 0;
            end
        end
        else begin
            LED_MATRIX[0] <= 8'h00;
            LED_MATRIX[1] <= 8'h00;
            LED_MATRIX[2] <= 8'h00;
            LED_MATRIX[3] <= 8'h00;

            // Check for reset signal
            RESYNC_BTN_RST <= {RESYNC_BTN_RST[2:0], BTN_RST == 0};
            
            if(~RESYNC_BTN_RST[3] & RESYNC_BTN_RST[2]) begin
                STOP <= 1;
                LED_MATRIX[3] <= 8'h18;
                BUCKET_POSITION <= 8'h04;
                RND <= 64'hA3D0_4F06_B2D4_9087;
            end
                
        end
    end

    always@(posedge CLK) begin
        case (COUNTER[11:10])
            2'b00: begin
                LED_R[7:0] <= ~LED_MATRIX[0];
                LED_C[3:0] <= ~4'b0001;
            end        
            2'b01: begin
                LED_R[7:0] <= ~LED_MATRIX[1];
                LED_C[3:0] <= ~4'b0010;
            end        
            2'b10: begin
                LED_R[7:0] <= ~LED_MATRIX[2];
                LED_C[3:0] <= ~4'b0100;
            end        
            2'b11: begin
                LED_R[7:0] <= ~LED_MATRIX[3];
                LED_C[3:0] <= ~4'b1000;
            end        
        endcase
    end
    
    always@(posedge CLK) begin
        COUNTER <= COUNTER + 1;
        TICK_COUNTER <= TICK_COUNTER + 1;
    end

    assign {LED_R7, LED_R6, LED_R5, LED_R4, LED_R3, LED_R2, LED_R1, LED_R0} = LED_R;
    assign {LED_C0, LED_C1, LED_C2, LED_C3} = LED_C;

endmodule