Implement basic scrolling in emu.js

emu.js

@@ -142,6 +142,8 @@ class Emulator {
 			this.cursor_move(1, 0);
 		} else if (e.key == 'Enter') {
 			this.cursor.y = this.range.end.y + 1;
+			if (this.cursor.y >= ROWS)
+				this.scroll();
 			this.cursor.x = 0;
 			this.submit_line();
 			Object.assign(this.range.start, this.cursor);
@@ -239,6 +241,8 @@ class Emulator {
 			this.grid[cell.y][cell.x] = this.grid[prev.y][prev.x];
 			cell = prev;
 		}
+		if (this.next_cell(this.range.end) == null)
+			this.scroll();
 		this.range.end = this.next_cell(this.range.end);
 	}
 
@@ -283,6 +287,14 @@ class Emulator {
 			return c;
 		}
 	}
+
+	scroll() {
+		this.grid.shift()
+		this.grid.push(new Array(COLS).fill(' '));
+		this.cursor.y -= 1;
+		this.range.start.y -= 1;
+		this.range.end.y -= 1;
+	}
 }
 
 window.addEventListener('DOMContentLoaded', () => {