body {
    margin: 0;
    padding: 0;
    background-color: #0f172a;
    font-family: 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
}

#header_section {
    margin-top: 0;
    height: 10vh;
    text-align: center;
    background-color: #1e293b;
    display: flex;
    justify-content: space-around;
    align-items: center;
    color: white;
}

#header_section button {
    border: none;
    background-color: #0f172a;
    font-size: x-large;
    color: white;
    padding: 7px 15px;
    border-radius: 10px;
    cursor: pointer;
    transition: 
        background-color 0.25s ease,
        transform 0.15s ease,
        box-shadow 0.25s ease;
}

#header_section button:hover {
    box-shadow: 0 0 12px rgba(255, 255, 255, 0.6);
    transform: translateY(-2px);
}

#header_section button:active {
    transform: scale(0.95);
    box-shadow: 0 0 5px rgba(59, 130, 246, 0.4);
    background-color: #172033;
}


#player1_section {
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: #2563eb;
    color: white;
    border-bottom-left-radius: 25px;
    border-bottom-right-radius: 25px;
    font-size: large;
}

#player2_section {
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: #dc2626;
    color: white;
    border-top-left-radius: 25px;
    border-top-right-radius: 25px;
    z-index: 1000;
    font-size: large;
}

#game-section {
  position: absolute;
  top: calc(50% + 40px);
  left: 50%;
  transform: translate(-50%, -50%);
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
}


#tic-tac-toe {
    background-color: #1e293b;
    width: 50vw;
    min-width: 300px;
    max-width: 500px;
    height: 50vw;
    min-height: 300px;
    max-height: 500px;
    padding: 10px;
    border-radius: 10px;
    display: grid;
    grid-template-columns: auto auto auto;
    gap: 7px;
}

.cell {
    background-color: rgb(218, 218, 218);
    transition: background-color 0.25s ease, transform 0.15s ease;
    border-radius: 10px;
    cursor: pointer;
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.cell:hover {
    background-color: #e5e7eb4f;
    transform: scale(1.02);
    box-shadow: 0 6px 18px rgba(0,0,0,0.12);
    box-shadow: inset 0 0 20px #ffffffc9; 
}

.cell:active {
    transform: scale(0.95);
}

@media (min-width: 768px) {
    #player1_section {
        position: fixed;
        height: 90vh;
        width: 100px;
        border-radius: 0 25px 25px 0;
        writing-mode: sideways-lr;
        font-size: x-large;
    }

    #player2_section {
        top: calc(0 + 10vh);
        right: 0;
        left: auto;
        bottom: auto;
        width: 100px;
        height: 90vh;
        border-radius: 25px 0 0 25px;
        writing-mode: sideways-rl;
        font-size: x-large;
    }
}