:root {
    --bg-color: #f9fafb;
    --header-color: #ffffff;
    --text-color: #1f2937;
    --secondary-text: #4b5563;
    --accent-color: #52a8c5;
    --accent-hover: #e0e0e0;
    --border-color: #e5e7eb;
    --button-bg: #52a8c5;
    --button-text: #1f2937;
    --button-hover-bg: #e0e0e0;
    --button-border: #d1d5db;
    --svg-bg: #f0f2f5;
    --svg-border: #cccccc;
    --footer-bg: #fafafa;
    --footer-text: #888888;
    --notification-bg: #000000;
    --notification-text: #ffffff;
    --input-border: #cccccc;
    --shadow-light: rgba(0, 0, 0, 0.05);
    --shadow-medium: rgba(0, 0, 0, 0.3);
    --input-bg: #ffffff;
    --grid-color: rgba(0, 0, 0, 0.05);
    --label-bg: #ffffff;
    --label-text: #000000;
    --stroke-color: black;
    --fill-color: black;
    --highlight-color: rgb(93, 0, 255);
    ;
}

body.dark-mode {
    --bg-color: #1e1e1e;
    --header-color: #2c2c2c;
    --text-color: #f0f0f0;
    --secondary-text: #d1d5db;
    --accent-color: #52a8c5;
    --accent-hover: #e0e0e0;
    --border-color: #3b3b3b;
    --button-bg: #0a799eab;
    --button-text: #f0f0f0;
    --button-hover-bg: #3a3a3a;
    --button-border: #444;
    --svg-bg: #2c2c2c;
    --svg-border: #444;
    --footer-bg: #1e1e1e;
    --footer-text: #999;
    --notification-bg: #ffffff;
    --notification-text: #000000;
    --input-border: #555;
    --shadow-light: rgba(255, 255, 255, 0.1);
    --shadow-medium: rgba(255, 255, 255, 0.2);
    --input-bg: #2a2a2a;
    --grid-color: rgba(255, 255, 255, 0.08);
    --label-bg: #474343;
    --label-text: #ffffff;
    --stroke-color: #cccccc;
    --fill-color: #e0e0e0;
    --highlight-color: rgb(19, 134, 134);
    ;
}

html,
body {
    height: 100%;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Roboto', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background-color: var(--header-color);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    text-align: center;
    box-shadow: 0 2px 4px var(--shadow-light);
}

h1 {
    font-size: 2rem;
    font-weight: 600;
    margin: 0;
    color: var(--text-color);
}

p {
    font-size: 1rem;
    color: var(--secondary-text);
    margin: 0.2rem 0;
}

.toggle-group {
    margin-top: 0.5rem;
    display: flex;
    gap: 1rem;
    align-items: center;
}

input[type="radio"] {
    accent-color: var(--accent-color);
}

.toggle-container {
    position: absolute;
    top: 1rem;
    right: 1.5rem;
    display: flex;
    gap: 0.5rem;
}

.toggle-button {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 42px;
    height: 42px;
    background-color: var(--button-bg);
    color: var(--button-text);
    border: 1px solid var(--button-border);
    border-radius: 6px;
    font-size: 1.4rem;
    cursor: pointer;
    padding: 6px;
    transition: background-color 0.2s, transform 0.2s;
}

.toggle-button:hover {
    background-color: var(--button-hover-bg);
    transform: scale(1.1);
}

.main-container {
    display: flex;
    padding: 1rem;
    gap: 1rem;
    flex: 1;
}

.actions-menu,
.test-menu,
.learn-menu {
    background-color: var(--header-color);
    padding: 1rem;
    border-radius: 12px;
    box-shadow: 0 2px 8px var(--shadow-light);
    width: 220px;
    flex-shrink: 0;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.actions-menu h2,
.test-menu h2,
.learn-menu h2 {
    font-size: 0.85rem;
    text-transform: uppercase;
    font-weight: 700;
    color: var(--accent-color);
    padding-left: 0.3rem;
    margin-top: 1rem;
    margin-bottom: 0.5rem;
    letter-spacing: 1px;
    position: relative;
}

.actions-menu h2::before,
.test-menu h2::before,
.learn-menu h2::before {
    content: "";
    position: absolute;
    left: 0;
    bottom: -4px;
    height: 2px;
    width: 100%;
    background: var(--accent-color);
    opacity: 0.3;
    border-radius: 2px;
}

.learn-menu {
    width: auto;
    margin-left: 16px;
    margin-right: 16px;
    box-sizing: border-box;
}

.learn-menu h1,
h3,
p {
    text-align: center;
    margin-top: 20px;
}

.problem-row {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    justify-content: space-evenly;
}

.problem {
    background-color: rgb(247, 246, 246);
    border-radius: 8px;
    padding: 1rem;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
    cursor: pointer;
    transition: box-shadow 0.2s ease;
    color: #333;
    flex: 1 1 200px;
    max-width: 500px;
}

.problem:hover {
    box-shadow: 0 4px 12px var(--button-hover-bg);
}

/* buttons apo learning section */
#problem-easy-btn,
#problem-medium-btn,
#problem-hard-btn {
    display: block;
    margin: 0 auto;
    margin-top: 20px;
    background: rgb(116, 199, 116);
}

#problem-medium-btn {
    background: rgb(204, 181, 80);
}

#problem-hard-btn {
    background: rgb(185, 86, 69);
}

button {
    background: linear-gradient(to right, #52a8c5, #4ca1af);
    color: white;
    font-weight: 600;
    border: none;
    border-radius: 10px;
    padding: 0.6rem 0.75rem;
    box-shadow: 0 2px 4px var(--shadow-light);
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.2s ease-in-out;
}

/* epiloges gia DFA/NFA apo learning section */
.tab-group-learning {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0;
    margin: 2rem 0 1.5rem 0;
    border-bottom: 2px solid var(--accent-color);
    width: 100%;
}

.tab-group-learning input[type="radio"] {
    display: none;
}

.tab-learning {
    padding: 0.8rem 2.5rem;
    background: none;
    color: var(--accent-color);
    font-weight: 700;
    font-size: 1.1rem;
    border: none;
    border-radius: 12px 12px 0 0;
    cursor: pointer;
    transition: background 0.2s, color 0.2s;
    margin-bottom: -2px;
    position: relative;
}

.tab-group-learning input[type="radio"]:checked+.tab-learning {
    background: var(--accent-color);
    color: #fff;
    box-shadow: 0 -2px 8px rgba(82, 168, 197, 0.10);
    z-index: 2;
}

.tab-learning:not(:first-child) {
    margin-left: 2px;
}

/* sto dark theme to text twn button exoun skia */
body.dark-mode button {
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.6);
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 10px var(--shadow-medium);
}

.user-icon-container {
    position: absolute;
    top: 1rem;
    left: 1.5rem;
    z-index: 10;
}

.user-icon {
    width: 32px;
    height: 32px;
    cursor: pointer;
}

#svg-area {
    flex-grow: 1;
    height: auto;
    min-height: 100%;
    margin: 0 0rem;
    position: relative;
    background-color: var(--svg-bg);
    box-shadow: inset 0 0 10px rgba(255, 255, 255, 0.05);
    /* grid */
    background-image: linear-gradient(var(--grid-color, rgba(0, 0, 0, 0.1)) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid-color, rgba(0, 0, 0, 0.1)) 1px, transparent 1px);
    background-size: 20px 20px;
    min-width: 3000px;
    display: block;
}

#svg-container {
    overflow-x: auto;
    overflow-y: hidden;
    width: 100%;
    flex-grow: 1;
    border: 2px dashed var(--svg-border);
    border-radius: 12px;
    background-color: var(--svg-bg);
    position: relative;
}

svg text {
    font-family: 'Fira Sans', Courier Prime;
}

#testStrings {
    padding: 0.4rem;
    font-size: 0.9rem;
    border: 1px solid var(--input-border);
    border-radius: 6px;
    margin-bottom: 0.5rem;
    background-color: var(--input-bg);
    color: var(--text-color);
}

#testResults {
    margin-top: 0.5rem;
    font-size: 0.95rem;
    color: var(--text-color);
}

footer {
    margin-top: auto;
    padding: 1rem;
    text-align: center;
    font-size: 0.85rem;
    background-color: var(--footer-bg);
    color: var(--footer-text);
    border-top: 1px solid var(--border-color);
}

#notification {
    position: absolute;
    top: 180px;
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--notification-bg);
    color: var(--notification-text);
    padding: 10px 20px;
    border-radius: 5px;
    display: none;
    z-index: 1000;
    font-size: 14px;
    box-shadow: 2px 2px 10px var(--shadow-medium);
}

.toggle-button img {
    width: 30px;
    height: 30px;
    display: block;
}

/* gia enallagh register/login */
.auth-tab {
    background-color: #cf1818;
    color: #1f2937;
    font-weight: 600;
    border: none;
    border-radius: 20px;
    padding: 0.5rem 1rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.auth-tab.active {
    background-color: #133541;
    color: white;
    box-shadow: 0 3px 6px rgba(0, 0, 0, 0.2);
    transform: scale(1.05);
}

.test-row {
    animation: fadeIn 0.3s ease-in;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(5px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.results-list {
    max-width: 100%;
    overflow-wrap: anywhere;
    word-break: break-word;
    list-style-position: inside;
    padding: 0;
    margin: 0;
}

.results-list li {
    display: flex;
    align-items: center;
    gap: 6px;
    margin-bottom: 6px;
    list-style: none;
    word-break: break-word;
    line-height: 1.4;
}

.results-list li::before {
    content: "•";
    font-size: 1rem;
    line-height: 1;
    color: var(--text-color);
    display: inline-block;
    transform: translateY(-1px);
}

.toggle-button img {
    width: 35px;
    height: 35px;
    object-fit: contain;
    pointer-events: none;
    display: block;
    margin: 0;
    padding: 0;
}

.toggle-button:hover img {
    transform: scale(1.1);
}

.state:hover {
    cursor: pointer;
}

.transition:hover {
    cursor: pointer;
}

.transition-label-bg {
    fill: var(--label-bg);
    stroke: var(--svg-border);
    stroke-width: 0.5;
    rx: 4;
    ry: 4;
    pointer-events: none;
    filter: drop-shadow(0px 1px 1px rgba(0, 0, 0, 0.2));
}

.transition-text {
    font-size: 14px;
    fill: var(--label-text);
    pointer-events: auto;
}