I paid full Steam price for these last weekend, oh well, them's the breaks I suppose.
Space Giraffe remains as truly awesome as ever of course (do not play it in the toned-down non-trippy mode, it destroys the essence of the game), Gridrunner however appears far less interesting, until you follow this sage advice (coped and pasted from the 'other' forum):
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They're not really comparable. Name and "enemies flying in from the borders" are about the only things the two games have in common.
GR++ is, I dunno, a more pure experience I suppose. You move your ship, you shoot shit, you collect sheep and try not to snuff it. It's not until you unlock the single life mode or thrusty that you'll get anything that's as close to that level of purity.
For best enjoyment, I'd recommend a few things:
Don't download the demo first for any other purposes than just seeing if it works. It'll give you no idea how the game will pan out and only runs shader 2.0 so it's not as pretty as the full game.
Destroy the soundtrack with furious fisty justice. BC's tips here -
http://yakyak.org/viewtopic.php?p=1418905#p1418905 - are a pain in the twat to work through but trust me, it's for the best. I threw in T2k/Space Giraffe's tunes instead of the ones shipped and having proper videogame music makes an enormous difference. I should really normalise the volumes, get the filesizes down a tad and bung that somewhere if I can ever be arsed.
Try not to smash your head through the screen at the worlds shittest unlock system. It's absolutely all over the shop so y'know, set some time aside to play through the parts you need to play through to open up the decent modes (ie - higher difficulties, thrusty and the single life mode), it'll only take about an hour and a bit to do the grunt work but you end up with a much better package then. You can play thrusty, the single life mode and Vindaloo/Phaal for proper shooty bang bangs and keep the rest of it for times you just want to mong out and make pretty colours on the screen.
Don't even contemplate playing it with a controller. It's designed for a mouse and really, it's the only way to play it unless you're crazy mental in the face.
Don't expect it to be a straightforward shooter. It's not. It's entirely about making pretty colours and scoring through making pretty colours. Which admittedly on the early difficulty levels pretty much boils down to "find a spot on the screen where your ship makes pretty colours and occasionally move to collect a sheep". Ignore that, it's much better on Vindaloo/Phaal and from around 12 onwards it'll start keeping you on your toes trying to get that score up.
Play thrusty mode. It's ace. Everyone should play thrusty mode.