Dreamcast Games That Support Rotation

The following Dreamcast games can be played on a monitor rotated to the vertical position.

Gunbird 2

VGA - Not Supported *
2 Player Mode - Simultaneous
DPad - Movement
A - Shot
B - Bomb
X - Close Attack
Y - Not Used **
L - Not Used
R - Rapid

a simple hex edit will enable VGA output but the game looks like turd)
while not used "in game" the "Y" button is required to select "2 Character mode (1p)" which allows you to alternate characters as a single player

Ikaruga

VGA - Supported
2 Player Mode - Simultaneous
DPad - Movement
A - Shot
B - Change
X - Not Used
Y - Not Used
L - Not Used
R - Release Power

Karous

VGA - Supported
2 Player Mode - None (Single Player Only)
DPad - Movement
A - Shot
B - Sword
X - DFS
Y - Not Used
L - Not Used
R - Not Used

Psyvariar II

VGA - Supported
2 Player Mode - None (Single Player Only)
DPad - Movement
A - Shot
B - Bomb
X - Not Used
Y - Not Used
L - Not Used
R - Not Used

Radilgy/Radirgy/Rajiruji

VGA - Supported
2 Player Mode - None (Single Player Only)
DPad - Movement
A - Shot
B - Sword
X - Absnet
Y - Not Used
L - Not Used
R - Not Used

Shikigami no Shiro II

VGA - Supported
2 Player Mode - Simultaneous
DPad - Movement
A - Shot
B - Bomb
X - Rapid
Y - Not Used
L - Not Used
R - Not Used

Triggerheart Exelica

VGA - Supported
2 Player Mode - None (Single Player Only)
DPad - Movement
A - Shot
B - Anchor
X - Not Used
Y - Not Used
L - Bomb
R - Bomb

Trizeal

VGA - Supported
2 Player Mode - Simultaneous
DPad - Movement
A - Shot
B - Trans
X - Bomb
Y - Rapid Shot
L - Not Used
R - Bomb

Under Defeat

VGA - Supported
2 Player Mode - Simultaneous
DPad - Movement
A - Shot
B - Bomb
X - Not Used
Y - Not Used
L - Not Used
R - Screen Mode*

• You probably don't want this button on your CP unless you want people to ask you to fix the game when they press it and the screen rotates back to horizontal and since your screen is now vertical the game is crooked.