:root {
    /* Dark Military Theme Variables */
    --color-bg-base: #2b2b2b;
    /* Dark background */
    --color-primary: #6b8e23;
    /* Olive drab for primary elements */
    --color-primary-light: #8ba870;
    /* Lighter olive */
    --color-primary-dark: #556b2f;
    /* Darker olive for hover/focus */
    --color-alert-bg: #3a3a3a;
    /* Darker alert background */
    --color-alert-border: #6b8e23;
    /* Same as primary */
    --color-text: #e0e0e0;
    /* Light text for contrast */
    --color-input-border: #555555;
    /* Muted border for inputs */
    --color-shadow: rgba(0, 0, 0, 0.8);
    /* Deeper shadow */
    --color-focus-ring: rgba(107, 142, 35, 0.5);
    /* Green focus ring */
    --color-white: #ffffff;
}

/* Base reset / global styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.base-body {
    background-color: var(--color-bg-base);
    color: var(--color-text);
    font-family: "Roboto", sans-serif;
    user-select: none;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2.5rem 0;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

/* Headings */
.heading-primary {
    font-size: 2.25rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 1.5rem;
    color: var(--color-primary-light);
}

.heading-secondary {
    font-size: 1.5rem;
    font-weight: 600;
    text-align: center;
    margin-bottom: 1rem;
    color: var(--color-text);
}

/* Alert */
.alert {
    background-color: var(--color-alert-bg);
    border-left: 4px solid var(--color-alert-border);
    color: var(--color-text);
    padding: 1rem;
    margin-bottom: 1.5rem;
}

.alert-title {
    font-weight: 700;
}

.alert-text {
    margin-top: 0.5rem;
}

/* Form Group */
.form-group {
    display: flex;
    justify-content: center;
    align-items: center;
    margin-bottom: 2rem;
}

/* Custom Number Input */
.custom-number-input {
    display: inline-flex;
    align-items: center;
    border: 1px solid var(--color-input-border);
    /* already defined */
    border-radius: 0.375rem;
    overflow: hidden;
    margin-right: 1rem;
    /* spacing between control and Generate button */
}

.custom-number-input .input-number {
    width: 4rem;
    border: none;
    text-align: center;
    background-color: var(--color-bg-base);
    color: var(--color-text);
    -moz-appearance: textfield;
    /* remove spinner in Firefox */
}

.custom-number-input .input-number::-webkit-outer-spin-button,
.custom-number-input .input-number::-webkit-inner-spin-button {
    -webkit-appearance: none;
    /* remove spinner in Chrome */
    margin: 0;
}

.custom-number-btn {
    background-color: var(--color-primary);
    color: var(--color-white);
    border: none;
    padding: 0.5rem;
    cursor: pointer;
    font-size: 1.25rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.custom-number-btn:hover {
    background-color: var(--color-primary-dark);
}


/* Button Primary */
.btn-primary {
    margin-left: 1rem;
    background-color: var(--color-primary);
    color: var(--color-white);
    padding: 0.5rem 1.5rem;
    border-radius: 0.375rem;
    box-shadow: 0 1px 2px var(--color-shadow);
    border: none;
    cursor: pointer;
    outline: none;
}

.btn-primary:hover {
    background-color: var(--color-primary-dark);
}

.btn-primary:focus {
    box-shadow: 0 0 0 2px var(--color-focus-ring);
}

/* Timer Display */
#timer-display {
    margin-left: 1rem;
    font-weight: bold;
    color: var(--color-text);
}

#timer-display::before {
    content: "⏰";
    margin-right: 0.4rem;
}

/* Board container */
.board-container {
    text-align: center;
}

/* Board status text */
.board-status {
    text-align: center;
    font-size: 1.125rem;
    color: var(--color-text);
    margin-bottom: 1.5rem;
}

/* Hide the "solved" text so your existing logic stays but it's invisible */
#solved {
    display: none;
    margin-bottom: 2rem;
    font-family: "Roboto", sans-serif;
    font-size: 1.5rem;
}

/* Overlay container covers the screen, hidden by default */
.overlay {
    display: none;
    position: fixed;
    z-index: 9999;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.75);
    justify-content: center;
    align-items: center;
}

.overlay.active {
    display: flex;
}

.overlay-content {
    background-color: var(--color-bg-base);
    padding: 2rem;
    border: 2px solid var(--color-primary);
    border-radius: 0.5rem;
    text-align: center;
    box-shadow: 0 0 15px var(--color-shadow);
}

.overlay-text {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-primary-light);
    margin-bottom: 1rem;
}

.overlay-button {
    background-color: var(--color-primary);
    color: var(--color-white);
    padding: 0.5rem 1.5rem;
    border-radius: 0.375rem;
    border: none;
    cursor: pointer;
    outline: none;
}

.overlay-button:hover {
    background-color: var(--color-primary-dark);
}