OpenTTD DS is a port of OpenTTD for Nintendo DS.

OpenTTD is a clone of the Microprose game “Transport Tycoon Deluxe”, a popular game originally written by Chris Sawyer. It attempts to mimic the original game as closely as possible while extending it with new features.

OpenTTD is licensed under the GNU General Public License version 2.0.

Changes:

based on r12452 (internal rev1926)
the NDS port now has a different toolbar, more suitable for the small screen
for better access with the touchscreen the toolbars have been moved to the bottom screen
a fully customizable on-screen keyboard has been added (click on a text field to open it)
a newsticker display on the lower screen has been added
some windows have been adapted for the NDS screen (more will follow in future releases):
– intro menu
– game creation menu
– minimap
– build vehicle window
when building depots and stations only one preview image is shown which you can rotate by clicking on it
information regarding accepted cargo when building a station is displayed as icons now
switching screens (left shoulder button L) now only switches the windows
many windows (e.g. confirmation dialogs) are now centered on the bottom screen
the amount of free ram (in kb) is displayed in the middle of the status bar. This is only a temporary change to help with tracking down a memory leak
additionally you can view some memory information by pressing the B button
always use new global pathfinder (NPF). the original TTD pathfinder crashes due to too many recursions
fixed loading screen glitch

http://www.tt-forums.net/viewtopic.php?f=33&t=35306&p=647762#p647762