Massachusetts' first casino, a slots parlor in Plainville, is set to open Wednesday, and it’s a prelude to more legal gambling on the way.

On Monday, the Plainridge Park Casino opened up to some invited guests for a sneak peak, and got some good reviews from its first guests for its ambiance, lack of smoke, food, cushiony carpets and wide aisles.

The large, open room, with high ceilings, is filled with 1,250 blinking, beeping, and chiming slot machines and electronic table games.

The invitees were mostly friends and family of casino workers, but there were also other gamblers on the casino’s radar screen who got an invitation in the mail. There were some happy moments at the slots, But there were a lot more ups and downs, and bad luck.

That’s fine with the casino. Vice President of Marketing Michelle Collins said the test day went pretty well.

“So far so good," Collins said. "We're just ironing out the glitches that you’d have for any opening. And we’re geared up for our Wednesday opening."

Massachusetts Gaming Commission member Jim McHugh said the state is allowing this first-ever casino to open in the state for two reasons.

"I think it means jobs and revenue," McHugh said. "And I think that was the intent of the legislature when they passed the expanded gaming bill."

The casino says it’s hired 609 people for opening day. And as for revenue, Plainridge Park is projected to bring in $80 million a year to the state, which will then go to cities and towns. Taxes will also support the state’s horse racing industry, some of which happens right here at Plainridge.

That expanded gaming bill also paved the way for casinos set to open in Springfield and Everett, as well as one in the southeastern part of the state. Projects in Brockton and New Bedford are currently vying for that license. McHugh says this slots parlor came first for a reason.

"Not only because it could be built more quickly and get the revenue stream going, but also because it was a modest-sized, relatively, facility that we could get up, get running, and learn from as we get on to the bigger facilities."

Expanded gambling in the state has raised some concerns.

"Statewide prevalence data for problem pathological gambling is 1.7 percent for any adults over the age of 18 in Massachusetts, so that equates to about 88,000 people in Massachusetts for past-year problems,” said Marlene Warner, executive director of the Massachusetts Council on Compulsive Gambling.

That’s why one feature of the new casino will be a booth dedicated to educating visitors about problem gambling. One of the booth workers approaches a casino visitor, holds out a bag of marbles, and asks her to pick one, which she calls the "un-winning marble."

Before the visitor can pick again, she has to put the marble back in the bag. And that’s the point. Her probability of picking a winning marble doesn’t go up with each pick, just like it doesn’t increase the more she pushes the button or pulls the lever of a slot machine. It’s a point that gamblers like Richard Ford of Boston take to heart.

"You have to be scientific in the way you play, kind of," Ford said. "Because basically, they’re here to get your money anyway. But you should not believe in hot slots or cold slots or anything. Or rub the machine like some people do. If it's going to pay, it's going to pay."

Beginning Wednesday, more gamblers will have the chance to find out if these slot machines will pay, as Massachusetts’ entry into legalized gambling begins.